The CD40-induced signaling pathway in endothelial cells resulting in the overexpression of vascular endothelial growth factor involves Ras and phosphatidylinositol 3-kinase

CD40 Ligand-CD40 Interaction Is an Intermediary between Inflammation and Angiogenesis in Proliferative Diabetic Retinopathy

We aimed to investigate the role of the CD40-CD40 ligand (CD40L) pathway in inflammation-mediated angiogenesis in proliferative diabetic retinopathy (PDR). We analyzed vitreous fluids and epiretinal fibrovascular membranes from PDR and nondiabetic patients, cultures of human retinal microvascular endothelial cells (HRMECs) and Müller glial cells and rat retinas with ELISA, immunohistochemistry, flow cytometry and Western blot analysis. Functional tests included measurement of blood-retinal barrier breakdown, in vitro angiogenesis and assessment of monocyte-HRMEC adherence. CD40L and CD40 levels were significantly increased in PDR vitreous samples. We demonstrated CD40L and CD40 expression in vascular endothelial cells, leukocytes and myofibroblasts in epiretinal membranes. Intravitreal administration of soluble (s)CD40L in normal rats significantly increased retinal vascular permeability and induced significant upregulation of phospho-ERK1/2, VEGF, intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). sCD40L induced upregulation of VEGF, MMP-9, MCP-1 and HMGB1 in cultured Müller cells and phospo-ERK1/2, p65 subunit of NF-ĸB, VCAM-1 and VEGF in cultured HRMECS. TNF-α induced significant upregulation of CD40 in HRMECs and Müller cells and VEGF induced significant upregulation of CD40 in HRMECs. sCD40L induced proliferation and migration of HRMECs. We provide experimental evidence supporting the involvement of the CD40L-CD40 pathway and how it regulates inflammatory angiogenesis in PDR.

Impact of CD40 gene polymorphisms on the risk of cervical squamous cell carcinoma: a case-control study

BACKGROUND

Cervical cancer is the fourth most common cancer among women worldwide. Genome-wide association studies have revealed multiple susceptible genes and their polymorphisms for cervical cancer risk. Therefore, we aimed to investigate the correlation between single nucleotide polymorphisms (SNPs) of the CD40 gene and susceptibility to cervical squamous cell carcinoma (CSCC) in a population from the northeastern Han Chinese population.

METHODS

The three SNPs (rs1800686, rs3765459, and rs4810485) of the CD40 gene were analyzed by multiplex polymerase chain reaction (PCR) combined with next-generation sequencing methods in 421 patients with CSCC, 594 patients with high-grade squamous intraepithelial lesions (HSIL), and 504 healthy females. Multivariate logistic regression analysis was used to analyze the potential relationship between CD40 gene polymorphisms and CSCC, or HSIL.

RESULTS

Our research results showed the AA genotype of rs1800686 had a protective effect on CSCC in comparison to the GG genotype and AG+GG genotypes (AA vs. GG: p = 0.0389 and AA vs. AG+GG: p = 0.0280, respectively). After FDR correction, the results were still statistically significant (p = 0.0389 and p = 0.0389, respectively). Similarly, rs3765459 showed a reduced risk association for CSCC in the codominant and recessive models (AA vs. GG: p = 0.0286 and AA vs. AG+GG: p = 0.0222, respectively). Significant differences remained after FDR correction (p = 0.0286 and p = 0.0286, respectively). However, these differences were no longer significant after the Bonferroni correction. In addition, the genotypes for the rs4810485 polymorphisms were associated with parity of the patients with CSCC. The genotypes for the rs3765459 polymorphisms were significantly correlated with the D-dimer of the patients with CSCC. The 3 SNPs genotypes of the CD40 gene were closely related to the squamous cell carcinoma antigen (SCC) of the patients with HSIL.

CONCLUSIONS

The CD40 gene may play a role in the occurrence and development of CSCC.

A radiologist’s guide to novel anticancer therapies in the era of precision medicine

Novel anticancer agents have replaced conventional chemotherapy as first line agents for many cancers, with continued new and expanding indications. Small molecule inhibitors act on cell surface or intracellular targets and prevent the downstream signaling that would otherwise permit tumor growth and spread. Anticancer antibodies can be directed against growth factors or may be immunotherapeutic agents. The latter act by inhibiting mechanisms that cancer cells use to evade the immune system. Hormonal agents act by decreasing levels of hormones that are necessary for the growth of certain cancer cells. Cancer therapy protocols often include novel anticancer agents and conventional chemotherapy used successively or in combination, in order to maximize survival and minimize morbidity. A working knowledge of anti-cancer drug classification will aid the radiologist in assessing response on imaging.

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Novel anticancer agents include small molecule inhibitors, antibodies and hormones.

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These agents are predominantly cytostatic and inhibit factors that provide a survival advantage to tumor cells.

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Modern cancer therapy employs a combination of novel anticancer agents and conventional chemotherapy.

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It is essential for radiologists to have a broad understanding of these agents and their mechanisms of action.

Development and Characterization of an Avirulent Leishmania major Strain

Leishmania major causes cutaneous leishmaniasis. An antileishmanial vaccine for humans is unavailable. In this study, we report development of two attenuated L. major strains-5ASKH-HP and LV39-HP-by continuous culture (high passage) of the corresponding virulent strains (low passage). Both avirulent strains showed similar changes in proteome profiles when analyzed by surface-enhanced laser desorption ionization mass spectrometry. Liquid chromatography-mass spectrometry and microarray characterization of 5ASKH strains revealed substantially altered gene and protein expression profiles, respectively. Both virulent and avirulent L. major strains grew comparably in culture, but the avirulent strain survived significantly less in BALB/c-derived peritoneal macrophages. Both attenuated strains failed to infect BALB/c mice and elicited IFN-γ, but not IL-4 and IL-10, responses. 5ASKH-HP parasites failed to induce significant infection even in severely immunocompromised- SCID or inducible NO synthase-, CD40-, or IL-12-deficient mice, indicating attenuation. The avirulent strain induced less IL-10, but higher IL-12, in macrophages. The avirulent strain failed to reduce CD40 relocation to the detergent-resistant membrane domain and to inhibit CD40-induced phosphorylation of the kinases Lyn and protein kinase C-β and MAPKs MKK-3/6 and p38MAPK or to upregulate MEK-1/2 and ERK-1/2 in BALB/c-derived peritoneal macrophages. The virulent and the avirulent strains reciprocally modulated CD40-induced Ras-mediated signaling through PI-3K and Raf-1. Avirulent 5ASKH-primed BALB/c mice were protected against virulent L. major challenge infection. The loss of virulence accompanied by substantially altered proteome profiles and the elicitation of host-protective immune responses indicate plausibly irreversible attenuation of the L. major strain and its potential use as a vaccine strain.

Tumor endothelial cell up-regulation of IDO1 is an immunosuppressive feed-back mechanism that reduces the response to CD40-stimulating immunotherapy

CD40-stimulating immunotherapy can elicit potent anti-tumor responses by activating dendritic cells and enhancing T-cell priming. Tumor vessels orchestrate T-cell recruitment during immune response, but the effect of CD40-stimulating immunotherapy on tumor endothelial cells has not been evaluated. Here, we have investigated how tumor endothelial cells transcriptionally respond to CD40-stimulating immunotherapy by isolating tumor endothelial cells from agonistic CD40 mAb- or isotype-treated mice bearing B16-F10 melanoma, and performing RNA-sequencing. Gene set enrichment analysis revealed that agonistic CD40 mAb therapy increased interferon (IFN)-related responses in tumor endothelial cells, including up-regulation of the immunosuppressive enzyme Indoleamine 2, 3-Dioxygenase 1 (IDO1). IDO1 was predominantly expressed in endothelial cells within the tumor microenvironment, and its expression in tumor endothelium was positively correlated to T-cell infiltration and to increased intratumoral expression of IFNγ. In vitro, endothelial cells up-regulated IDO1 in response to T-cell-derived IFNγ, but not in response to CD40-stimulation. Combining agonistic CD40 mAb therapy with the IDO1 inhibitor epacadostat delayed tumor growth in B16-F10 melanoma, associated with increased activation of tumor-infiltrating T-cells. Hereby, we show that the tumor endothelial cells up-regulate IDO1 upon CD40-stimulating immunotherapy in response to increased IFNγ-secretion by T-cells, revealing a novel immunosuppressive feedback mechanism whereby tumor vessels limit T-cell activation.

Ras isoforms: signaling specificities in CD40 pathway

Background

Ras are small cellular GTPases which regulate diverse cellular processes. It has three isoforms: H-Ras, K-Ras, and N-Ras. Owing to the N-terminus (1–165 residues) sequence homology these isoforms were thought to be functionally redundant. However, only K-Ras-deficient mice but not H-Ras- and N-Ras-deficient mice show embryonic lethality. Similarly, mutations in a given Ras isoform are associated with a particular type of cancer. Moreover, we have previously reported that Ras isoforms perform unique functions in Leishmania major infection. Thus, Ras isoforms are implicated to have signaling and functional specificity but the mechanism remains to be elucidated.

Result

Using CD40 as a model receptor, we showed that depending on the strength of signaling, specific Ras isoforms are activated. Weak CD40 signal activates N-Ras, whereas strong signal activates H-Ras and K-Ras. Additionally, we showed that suppression of N-Ras expression reduced CD40-induced extracellular signal–regulated kinase-1/2 (ERK-1/2) activation and Interleukin (IL)-10 production; whereas suppression of H-Ras or K-Ras reduced CD40-induced p38 mitogen-activated protein kinase (p38MAPK) activation and IL-12 production. Furthermore, we showed that Ras isoforms have activator (GEF) specificity as weak CD40 signal-activated N-Ras requires Sos-1/2 whereas strong CD40 signal-activated H-Ras/K-Ras requires Ras-GRP as the guanine-nucleotide exchange factor (GEF) inducing ERK-1/2- or p38MAPK-mediated IL-10 or IL-12 productions, respectively, in macrophages. Silencing of syk reduced CD40-induced N-Ras activation but silencing of lyn inhibited H-Ras and K-Ras activation. In CD40 signaling, Ras isoforms also showed effector specificity; while H-Ras and K-Ras showed specificity for phosphatidyl inositol-3 kinase activation at high dose of CD40 stimulation, N-Ras primarily associated with Raf-1 at low dose of CD40 stimulation. Moreover, fractal analysis showed that functional site surface roughness for H-Ras (SurfaceFD = 2.39) and K-Ras (SurfaceFD = 2.39) are similar but significantly different from N-Ras (SurfaceFD = 2.25).

Conclusion

The activator and effector specificities of Ras isoforms in CD40 signaling indicated their differential involvement in CD40 pathway and in maintaining the reciprocity. Our observations reveal Ras-regulated signaling outcome and its potential for developing Ras isoform-targeted immunotherapy and prophylaxis.

Graphical abstract

Modulation of Immunosuppression by Oligonucleotide-Based Molecules and Small Molecules Targeting Myeloid-Derived Suppressor Cells

Myeloid-derived suppressor cells (MDSCs) are immature myeloid cells that exert suppressive function on the immune response. MDSCs expand in tumor-bearing hosts or in the tumor microenvironment and suppress T cell responses via various mechanisms, whereas a reduction in their activities has been observed in autoimmune diseases or infections. It has been reported that the symptoms of various diseases, including malignant tumors, can be alleviated by targeting MDSCs. Moreover, MDSCs can contribute to patient resistance to therapy using immune checkpoint inhibitors. In line with these therapeutic approaches, diverse oligonucleotide-based molecules and small molecules have been evaluated for their therapeutic efficacy in several disease models via the modulation of MDSC activity. In the current review, MDSC-targeting oligonucleotides and small molecules are briefly summarized, and we highlight the immunomodulatory effects on MDSCs in a variety of disease models and the application of MDSC-targeting molecules for immuno-oncologic therapy.

Comparison of the Effect of Two Hyaluronic Acid Preparations on Fibroblast and Endothelial Cell Functions Related to Angiogenesis

Hyaluronic acid (HA) is used in substitutive and aesthetic medicine with various applications. Ultrapure absorbable HA (Bioregen^®) and a mix of reticulated and free low molecular weight HA (Regenyal Idea Bioexpander®) (both provided by Regenyal Laboratories Srl, San Benedetto del Tronto (AP), Italy) represent a reliable hydrating device and skin filler, useful for skin blemishes, lines and wrinkles, and lip widening, respectively. The commercial products are known for their safety, but data on the molecular, cellular, and tissue responses are lacking. We aimed to evaluate the bioavailability and the pro-angiogenic features of the products Bioregen^® and Bioexpander^® in vitro on cultured endothelial cells (ECs) and dermal fibroblasts in vivo when injected into experimental animals. When added to fibroblasts and ECs, Bioexpander^® induced cell migration. The two HA preparations were well tolerated, while a transient proangiogenic behavior of Bioexpander^®, when implanted subcutaneously in mice, was found. The neovascular response was evident in the first week with higher levels of VEGF and FGF-2 before undergoing regression. In conclusion, our data strengthen the safety of HA synthetic preparations both in vitro and in vivo. Even if a proangiogenic response is documented, it is modest and transient, leading to tissue recovery and absence of an inflammatory infiltrate.

Noncanonical NF-κB signaling in microvessels of atherosclerotic lesions is associated with inflammation, atheromatous plaque morphology and myocardial infarction

BACKGROUND AND AIMS

Neovascularization is associated with atherosclerotic plaque instability and increased chance of myocardial infarction (MI). Patients with chronic inflammatory diseases (CID) have increased risk of atherosclerosis, and evidence demonstrates that NF-κB inducing kinase (NIK)-mediated noncanonical NF-κB signaling in endothelial cells (EC) is linked to inflammation and angiogenesis. Here, we hypothesized NIK may also be activated in EC of atherosclerotic lesion microvessels.

METHODS

Using cohorts of atherosclerotic lesions from coronary and carotid arteries, we quantified NIK expression in plaque microvessels and compared it to pathological markers, including inflammatory cell content, plaque characteristics and MI. Differences in gene transcripts were evaluated between stable and ruptured lesions.

RESULTS

NIK+EC were present in both coronary and carotid lesions. In CID patients, plaques with stenosis >40% had an increased number of NIK+EC and higher content of immune cells (p < .05) as compared to controls. Immune cells per NIK+EC were also greater in CID patients (p < .05), with pronounced differences as stenosis increased. In unstable lesions, NIK+EC were elevated as were EC expressing CXCL12 (p < .05). NIK+EC were increased in lesions with lipid content >40% (p < .05) and more abundant in coronary artery lesions implicated in MI (p < .05). These vessels also associated with atheromatous rather than fibrous plaque morphology (p < .05). Transcriptomic profiling demonstrated components of noncanonical NF-κB pathway were also upregulated in ruptured plaques (p < .05).

CONCLUSIONS

NIK+EC associate with chronic inflammation in advanced lesions and are linked to markers of local inflammation, lipid content, unstable plaque phenotype and development of MI. Therefore, targeting noncanonical NF-κB signaling may hold therapeutic potential for patients with atherosclerosis and cardiovascular disease.

Sunitinib enhances the antitumor responses of agonistic CD40-antibody by reducing MDSCs and synergistically improving endothelial activation and T-cell recruitment

CD40-activating immunotherapy has potent antitumor effects due to its ability to activate dendritic cells and induce cytotoxic T-cell responses. However, its efficacy is limited by immunosuppressive cells in the tumor and by endothelial anergy inhibiting recruitment of T-cells. Here, we show that combining agonistic CD40 monoclonal antibody (mAb) therapy with vascular targeting using the tyrosine kinase inhibitor sunitinib decreased tumor growth and improved survival in B16.F10 melanoma and T241 fibrosarcoma. Treatment of tumor-bearing mice with anti-CD40 mAb led to increased activation of CD11c+ dendritic cells in the tumor draining lymph node, while sunitinib treatment reduced vessel density and decreased accumulation of CD11b+Gr1+ myeloid derived suppressor cells. The expression of ICAM-1 and VCAM-1 adhesion molecules was up-regulated on tumor endothelial cells only when anti-CD40 mAb treatment was combined with sunitinib. This was associated with enhanced intratumoral infiltration of CD8+ cytotoxic T-cells. Our results show that combining CD40-stimulating immunotherapy with sunitinib treatment exerts potent complementary antitumor effects mediated by dendritic cell activation, a reduction in myeloid derived suppressor cells and increased endothelial activation, resulting in enhanced recruitment of cytotoxic T-cells.

Propolis and swimming in the prevention of atherogenesis and left ventricular hypertrophy in hypercholesterolemic mice

AIMS

The present study verified the effect of propolis alone and its association with swimming in dyslipidemia, left ventricular hypertrophy and atherogenesis of hypercholesterolemic mice.

METHODS AND RESULTS

The experiments were performed in LDLr-/- mice, fed with high fat diet for 75 days, and were divided into four experimental groups (n=10): HL, sedentary, subjected to aquatic stress (5 min per day, 5 times per week); NAT submitted to a swimming protocol (1 hour per day, 5 times per week) from the 16th day of the experiment; PRO, sedentary, submitted to aquatic stress and which received oral propolis extract (70 uL/animal/day) from the 16th day of the experiment; HL+NAT+PRO, submitted to swimming and which received propolis as described above. After 75 days, blood was collected for analysis of serum lipids. The ratio between the ventricular weight (mg) and the animal weight (g) was calculated. Histological sections of the heart and aorta were processed immunohistochemically with anti-CD40L antibodies to evaluate the inflammatory process; stained with hematoxylin/eosin and picrosirius red to assess morphological and morphometric alterations. The HL animals showed severe dyslipidemia, atherogenesis and left ventricular hypertrophy, associated with a decrease in serum HDLc levels and subsequent development of cardiovascular inflammatory process, characterized by increased expression of CD40L in the left ventricle and aorta. Swimming and propolis alone and\or associated prevented the LVH, atherogenesis and arterial and ventricular inflammation, decreasing the CD40L expression and increasing the HDLc plasmatic levels.

CONCLUSION

Propolis alone or associated with a regular physical activity is beneficial in cardiovascular protection through anti-inflammatory action.

Regulation of mTOR Signaling by Semaphorin 3F-Neuropilin 2 Interactions In Vitro and In Vivo

Semaphorin 3F (SEMA3F) provides neuronal guidance cues via its ability to bind neuropilin 2 (NRP2) and Plexin A family molecules. Recent studies indicate that SEMA3F has biological effects in other cell types, however its mechanism(s) of function is poorly understood. Here, we analyze SEMA3F-NRP2 signaling responses in human endothelial, T cell and tumor cells using phosphokinase arrays, immunoprecipitation and Western blot analyses. Consistently, SEMA3F inhibits PI-3K and Akt activity, and responses are associated with the disruption of mTOR/rictor assembly and mTOR-dependent activation of the RhoA GTPase. We also find that the expression of vascular endothelial growth factor, as well as mTOR-inducible cellular activation responses and cytoskeleton stability are inhibited by SEMA3F-NRP2 interactions in vitro. In vivo, local and systemic overproduction of SEMA3F reduces tumor growth in NRP2-expressing xenografts. Taken together, SEMA3F regulates mTOR signaling in diverse human cell types, suggesting that it has broad therapeutic implications.

Small GTPase and regulation of inflammation response in atherogenesis

Small GTPases are key signal transducers from extracellular stimuli to the nucleus that regulate a variety of cellular responses, including changes in gene expression and cell adhesion and migration. Accumulating data have demonstrated that abnormal activation of these small GTPases plays a critical role in the atherosclerosis characterized by vascular abnormalities, especially endothelial dysfunction and inflammation. Here, we discuss the linkage between small GTPases, inflammation, and atherogenesis. First, small GTPases affect gene expression of inflammatory cytokines through proinflammatory signaling pathways, such as nuclear factor-κB, vascular cell adhesion molecule-1, intercellular adhesion molecule-1, interlukin-8, and monocyte chemoattractant protein-1. Then, these molecules regulate the vascular inflammation through cell adhesion and migration. In turn, small GTPases are also regulated by extracellular stimuli, such as L-selectin, thrombin, oxidized phospholipids, and interleukins. Thus, these inflammatory cytokines generate a vicious cycle for small GTPases and inflammatory responses in the atherogenesis.

The relationship between intervention in the CD40 signal pathway and choroidal neovascularization

Age-related macular degeneration, pathologic myopia, ocular trauma, and other eye diseases can cause choroidal neovascularization (CNV). In recent years, photodynamic therapy (PDT), anti-vascular endothelial growth factor (anti-VEGF) medications, laser treatment, and other measures against CNV have been gradually applied in the clinical setting and in some cases have achieved good results. However, the pathogenesis of CNV has not been fully elucidated. The costimulatory system made up of cluster of differentiation 40 protein (CD40) and its ligand (CD40L) is an important signal transduction pathway among immune cells. The activation of CD40 can also stimulate the secretion of a variety of angiogenic growth factors (eg, VEGF) and basic fibroblast growth factors that might lead to CNV. The high level expression of CD40 and CD40L has been detected in CNV diseases. Interference with the CD40 signaling pathway may become a new target for CNV treatment. We review the relationship between CD40, CD40L, and CNV.

Protective effects of hydrogen-rich saline on ulcerative colitis rat model

BACKGROUND

Ulcerative colitis (UC) is associated with enhanced production of reactive oxygen species and altered angiogenesis. Molecular hydrogen has been documented as a novel antioxidant to treat various reactive oxygen species-related diseases. The present study aimed to investigate the effects of hydrogen on UC using a rat model.

MATERIALS AND METHODS

UC in rats was induced with intracolonically administrated acetic acid. Hydrogen was supplied through intraperitoneal injection of 10 or 20 mL/kg hydrogen-rich saline. The hydrogen treatment was performed once every 2 d and lasted 2 wk. The stool consistency and weight loss were used to evaluate UC development. Colonic mucosal damage at the end of the experiment was scored using the macroscopic and microscopic observations. Vascular endothelial growth factor expression in the colonic mucosa was determined using immunohistochemistry.

RESULTS

The administration of acetic acid induced acute rat UC, as indicated by diarrhea, weight loss, and colonic mucosal damage. Treatment with hydrogen-rich saline reduced the weight loss and diarrhea and alleviated the colonic mucosal damage in the UC rats. In addition, the expression of vascular endothelial growth factor in the UC rats increased and could be inhibited by hydrogen treatment.

CONCLUSIONS

Antioxidative hydrogen-rich saline effectively protected the rats from UC, which might be, at least in part, because of inhibition of vascular endothelial growth factor.

TRAF6 inhibits proangiogenic signals in endothelial cells and regulates the expression of vascular endothelial growth factor

TNF-family molecules induce the expression Vascular Endothelial Growth Factor (VEGF) in endothelial cells (EC) and elicit signaling responses that result in angiogenesis. However, the role of TNF-receptor associated factors (TRAFs) as upstream regulators of VEGF expression or as mediators of angiogenesis is not known. In this study, HUVEC were cotransfected with a full-length VEGF promoter-luciferase construct and siRNAs to TRAF 1, -2, -3, -5, -6, and promoter activity was measured. Paradoxically, rather than inhibiting VEGF expression, we found that knockdown of TRAF6 resulted in a 4-6-fold increase in basal VEGF promoter activity compared to control siRNA-transfected EC (P<0.0001). In addition, knockdown of TRAF 1, -2, -3 or -5 resulted in a slight increase or no change in VEGF promoter activation. Using [(3)H]thymidine incorporation assays as well as the in vitro wound healing assay, we also found that basal rates of EC proliferation and migration were increased following TRAF6 knockdown; and this response was inhibited by the addition of a blocking anti-VEGF antibody into cell cultures. Using a limited protein array to gain insight into TRAF6-dependent intermediary signaling responses, we observed that TRAF6 knockdown resulted in an increase in the activity of Src family kinases. In addition, we found that treatment with AZD-0530, a pharmacological Src inhibitor, reduced the regulatory effect of TRAF6 knockdown on VEGF promoter activity. Collectively, these findings define a novel pro-angiogenic signaling response in EC that is regulated by TRAF6.

Glucotoxicity and α cell dysfunction: involvement of the PI3K/Akt pathway in glucose-induced insulin resistance in rat islets and clonal αTC1-6 cells

AIM/HYPOTHESIS

The objective of this study was to assess how long-term exposure to high glucose affects the α cell function and whether the increased glucagon secretion is mediated via insulin resistance.

MATERIALS AND METHODS

We established a β cell-depleted rat model to obtain pure primary α cells. Furthermore, isolated rat islets and TC1-6 cells (a clonal α cell line) were exposed to high glucose (25 or 30 mmol/L) and low glucose (5.5 mmol/L) for up to 5 days to evaluate the influence of chronic glucose toxicity on glucagon secretion and glucagon gene expression. Moreover, we added insulin and/or Wortmannin to examine if the inhibitory effect of insulin on glucagon secretion was impaired by high glucose via the phosphatidylinositol 3 kinase/PKB protein kinase B pathway.

RESULTS

Both glucagon secretion and glucagon gene expression were increased in response to 5 days exposure to high glucose. While a moderate insulin concentration slightly inhibits glucagon secretion from rat islets and α TC1-6 cells at high glucose, a pronounced increase in glucagon secretion was observed at low glucose. We found that the insulin-mediated activity of the phosphatidylinositol 3 kinase/PKB protein kinase B pathway in the α cell was markedly impaired by chronic exposure to high glucose.

CONCLUSION

The hypersecretion of glucagon induced by glucotoxicity may be secondary to insulin resistance of the α cell induced by impaired activity of the insulin signaling pathway.

Association of CD40 gene polymorphisms with sporadic breast cancer in Chinese Han women of Northeast China

Background

Breast cancer is a polygenetic disorder with a complex inheritance pattern. Single nucleotide polymorphisms (SNPs), the most common genetic variations, influence not only phenotypic traits, but also interindividual predisposition to disease, treatment outcomes with drugs and disease prognosis. The co-stimulatory molecule CD40 plays a prominent role in immune regulation and homeostasis. Accumulating evidence suggests that CD40 contributes to the pathogenesis of cancer. Here, we set out to test the association between polymorphisms in the CD40 gene and breast carcinogenesis and tumor pathology.

Methodology and Principal Findings

Four SNPs (rs1800686, rs1883832, rs4810485 and rs3765459) were genotyped by the polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) method in a case-control study including 591 breast cancer patients and 600 age-matched healthy controls. Differences in the genotypic distribution between breast cancer patients and healthy controls were analyzed by the Chi-square test for trends. Our preliminary data showed a statistically significant association between the four CD40 gene SNPs and sporadic breast cancer risk (additive P = 0.0223, 0.0012, 0.0013 and 0.0279, respectively). A strong association was also found using the dominant, recessive and homozygote comparison genetic models. In the clinical features analysis, significant associations were observed between CD40 SNPs and lymph node metastasis, human epidermal growth factor receptor 2 (C-erbB2), estrogen receptor (ER), progesterone receptor (PR) and tumor protein 53 (P53) statuses. In addition, our haplotype analysis indicated that the haplotype C_rs1883832G_rs4810485, which was located within the only linkage disequilibrium (LD) block identified, was a protective haplotype for breast cancer, whereas T_rs1883832T_rs4810485 increased the risk in the studied population, even after correcting the P value for multiple testing (P = 0.0337 and 0.0430, respectively).

Conclusions and Significance

Our findings primarily show that CD40 gene polymorphisms contribute to sporadic breast cancer risk and have a significant association with clinicopathological features among Chinese Han women from the Heilongjiang Province.

The role of RPE cell-associated VEGF₁₈₉ in choroidal endothelial cell transmigration across the RPE

PURPOSE

To determine the role of vascular endothelial growth factor 189 (VEGF₁₈₉) in choroidal endothelial cell (CEC) migration across the retinal pigment epithelium (RPE) and to explore the molecular mechanisms involved.

METHODS

Using real-time PCR, the expression of VEGF splice variants VEGF₁₂₁, VEGF₁₆₅, and VEGF₁₈₉ was determined in human RPE from donor eyes, cultured human RPE in contact with CECs exposed to hydrogen peroxide (H₂O₂) or hypoxia, and RPE/choroid specimens from mice treated with laser to induce choroidal neovascularization (CNV). Activation of VEGF receptors (VEGFRs), phosphoinositol 3-kinase (PI-3K) or Rac1 was measured in CECs cocultured in contact with RPE exposed to peroxide or silenced for VEGF₁₈₉ expression. Migration of CECs across the RPE was determined using fluorescence microscopy.

RESULTS

VEGF₁₈₉ expression was increased in human RPE from aged compared with young donor eyes and from mouse RPE/choroids after laser to induce CNV. VEGF₁₈₉ was also upregulated in human RPE challenged with peroxide, hypoxia, or cultured in contact with CECs. CEC migration across RPE was greater after RPE exposure to peroxide to induce VEGF₁₈₉; VEGFR2 and Rac1 activities were also increased in these CECs. When CECs were cocultured with RPE silenced for VEGF₁₈₉, VEGFR2 and Rac1 activities in CECs were significantly reduced, as was CEC migration across the RPE. Inhibition of Rac1 activity significantly inhibited CEC transmigration without affecting PI-3K activity.

CONCLUSIONS

RPE-derived cell-associated VEGF₁₈₉ facilitates CEC transmigration by Rac1 activation independently of PI-3K signaling and may have importance in the development of neovascular AMD.

Altered VEGF mRNA stability following treatments with immunosuppressive agents: implications for cancer development

The high incidence of cancer and its aggressive progression is a common and major problem in patients receiving immunosuppressive therapy. The calcineurin inhibitors (CNIs) may have protumorigenic effects and can promote the overexpression of several molecules inducing tumor growth. We have recently demonstrated that CNIs can mediate the transcriptional activation of the angiogenic cytokine vascular endothelial growth factor (VEGF) and promote a rapid progression of human renal cancer. Here, we investigated whether the CNI cyclosporine (CsA) and the mTOR inhibitor rapamycin (RAPA) could alter the mRNA stability of VEGF in 786-0 and Caki-1 renal cancer cells. Following actinomycin D treatment, we observed that CsA increased, whereas RAPA decreased the VEGF mRNA stability as observed by real time PCR. It is established that the mRNA-binding protein HuR may play a critical role in VEGF mRNA stability. By using HuR-siRNA, we found that the knockdown of HuR significantly decreased the CNI-induced VEGF mRNA stability. By Western blot analysis, it has been observed that CNI treatment induced the translocation of HuR from the nucleus to the cytoplasm; CNIs also induced the association between HuR and PKC-delta and promoted the phosphorylation of HuR. Finally, we found that the inhibition of PKC-delta using a dominant negative plasmid significantly decreased the CsA-induced cytoplasmic translocation of HuR and VEGF mRNA stability. Together, targeting the pathways that promote CNI-induced transcription as well as the mRNA stability of VEGF might serve as novel therapeutics for the prevention and treatment of cancer in immunosuppressed patients.

Phosphoinositide 3-kinase mediates CD40 ligand-induced oxidative stress and endothelial dysfunction via Rac1 and NADPH oxidase 2

OBJECTIVES

CD40 ligand (CD40L) has been implicated as an inducer of reactive oxygen species (ROS) generation in endothelial cells, but definitive evidence for this and the in vivo relevance haves not been demonstrated fully. We thus investigated whether phosphoinositide 3-kinase (PI3K) was linked to ROS generation and endothelial reactivity in response to CD40L.

METHODS AND RESULTS

CD40L treatment activated PI3K activity by regulating the association between PI3K p85 and the CD40 receptor. CD40L exposure also stimulated the GTPase Rac1, which is known to activate NADPH oxidases, and enhanced ROS formation, whereas PI3K inhibition or depletion by small interfering RNA (siRNA) prevented these responses. Subsequently, PI3K overexpression activated Rac1 and increased ROS generation. These responses were not observed in the presence of inactive Rac1 or siRNA against the NADPH oxidase subunit NOX2. Protein kinase Czeta mediates PI3K-regulated NADPH oxidase activation by promoting cellular p47phox translocation. Importantly, PI3K inhibition prevented CD40L-mediated ROS generation and endothelial dysfunction in a mouse model. In summary, PI3K mediates CD40L-induced ROS production and subsequent endothelial dysfunction.

CONCLUSIONS

Targeting PI3K may provide a new therapeutic approach in diseases associated with oxidative stress and endothelial dysfunction.

Therapeutic interventions targeting CD40L (CD154) and CD40: the opportunities and challenges

CD40 was originally identified as a receptor on B-cells that delivers contact-dependent T helper signals to B-cells through interaction with CD40 ligand (CD40L, CD154). The pivotal role played by CD40-CD40L interaction is illustrated by the defects in B-lineage cell development and the altered structures of secondary lymphoid tissues in patients and engineered mice deficient in CD40 or CD40L. CD40 signaling also provides critical functions in stimulating antigen presentation, priming of helper and cytotoxic T-cells and a variety of inflammatory reactions. As such, dysregulations in the CD40-CD40L costimulation pathway are prominently featured in human diseases ranging from inflammatory conditions to systemic autoimmunity and tissue-specific autoimmune diseases. Moreover, studies in CD40-expressing cancers have provided convincing evidence that the CD40-CD40L pathway regulates survival of neoplastic cells as well as presentation of tumor-associated antigens to the immune system. Extensive research has been devoted to explore CD40 and CD40L as drug targets. A number of anti-CD40L and anti-CD40 antibodies with diverse biological effects are in clinical development for treatment of cancer and autoimmune diseases. This chapter reviews the role of CD40-CD40L costimulation in disease pathogenesis, the characteristics of therapeutic agents targeting this pathway and status of their clinical development.

CD40-induced signaling in human endothelial cells results in mTORC2- and Akt-dependent expression of vascular endothelial growth factor in vitro and in vivo

We have examined CD40-dependent signals in endothelial cells (EC) mediating the expression of vascular endothelial growth factor (VEGF) and VEGF-induced angiogenesis. We treated confluent cultures of EC with soluble CD40L (sCD40L), and by Western blot found a marked increase in the phosphorylation of Akt, 4EBP-1, and S6K1, compared with untreated cells. EC were transfected with a full-length VEGF promoter-luciferase construct and cultured in the absence or presence of rapamycin and sCD40L. We found that rapamycin, which blocks mTORC1 and mTORC2 signaling, inhibited sCD40L-mediated transactivation of VEGF. In addition, by Western blot, we found that the transfection of EC with small interfering RNA (siRNA) to rictor (to inhibit mTORC2), and not raptor (to inhibit mTORC1), inhibited sCD40L-dependent protein expression of VEGF. In additions, we found that basal levels of phosphorylated Akt as well as VEGF were increased in EC transfected with the raptor siRNA. Also, rapamycin failed to inhibit VEGF promoter activation, as well as VEGF protein expression in EC transfected with a constitutively active construct of Akt, further demonstrating that mTORC1 is not necessary for CD40- and Akt-induced expression of VEGF. Finally, we injected human CD40L-transfected fibroblasts or mock transfectants into human skin on SCID mice. We found that the injection of CD40L transfectants, but not mock cells, resulted in VEGF expression and mediated a marked angiogenesis reaction, and this response was reduced in mice treated with rapamycin. Together, these observations indicate that mTORC2 and Akt facilitate CD40-inducible expression of VEGF in EC, which is of clinical importance in tumor growth and the progression of chronic inflammatory diseases.

Inhibition of CD40-CD154 costimulatory pathway by a cyclic peptide targeting CD154

Disruption of the CD40-CD154 interaction was found to be effective in the prevention and treatment of several immune-mediated diseases. The antibody-based strategy of inhibition was in humans limited by platelet activation leading to thrombotic effects. Other strategies different from antibody technology may be useful to create tools to interfere with CD40-CD154 pathway. In the present study, we selected and characterized from a phage display library, cyclic hepta-peptides specific for human CD154 through biopanning against plate-immobilized recombinant hCD154-muCD8. Nine phage clones were selected for the ability to bind CD154 expressed on the surface of J558L cells transfected with human CD154. From the nine selected phage clones, we obtained seven different amino acidic sequences, and the corresponding hepta-peptides rendered cyclic by two cysteines were synthesized. All the peptides specifically bound CD154 expressed on J558L. However, only the peptide 4.10 (CLPTRHMAC) was found to recognize the active binding site of CD154, as it competed with the blocking anti-CD154 antibody. When changes in the amino acid composition were introduced in the sequence of 4.10 peptide, the binding to CD154 was abrogated, suggesting that the amino acid sequence was critical for its specificity. This peptide was found to inhibit the CD40-CD154 interaction, preventing CD40-dependent activation of B lymphocytes in vitro as it was able, as the blocking anti-human CD154 mAb, to prevent the expression of CD80 and CD86 costimulatory molecules and switching of Ig isotype induced by CD154. Moreover, the peptide 4.10 inhibited the in vitro endothelial cell motility and organization into capillary-like structures, and the in vivo angiogenesis of human umbilical cord-derived endothelial cells implanted in Matrigel in severe combined immunodeficiency mice. In vitro studies on platelet activation demonstrated that the 4.10 peptide, at variance of the anti-CD154 mAb, was unable to prime human platelet activation and aggregation. In conclusion, we identify a cyclic hepta-peptide able to displace the binding of human CD154 to CD40 expressed on cell surface and to abrogate some biological effects related to the CD40 stimulation, such as B cell activation and endothelial triggered angiogenesis.

Soluble CD40 ligand induces endothelial dysfunction in human and porcine coronary artery endothelial cells

The purpose of this study was to determine the effects and mechanisms of sCD40L on endothelial dysfunction in both human coronary artery endothelial cells (HCAECs) and porcine coronary artery rings. HCAECs treated with sCD40L showed significant reductions of endothelial nitric oxide synthase (eNOS) mRNA and protein levels, eNOS mRNA stability, eNOS enzyme activity, and cellular NO levels, whereas superoxide anion (O(2)(-)) production was significantly increased. sCD40L enhanced eNOS mRNA 3'UTR binding to cytoplasmic molecules and induced a unique expression pattern of 95 microRNAs. sCD40L significantly decreased mitochondrial membrane potential, and catalase and SOD activities, whereas it increased NADPH oxidase (NOX) activity. sCD40L increased phosphorylation of MAPKs p38 and ERK1/2 as well as IkappaBalpha and enhanced NF-kappaB nuclear translocation. In porcine coronary arteries, sCD40L significantly decreased endothelium-dependent vasorelaxation and eNOS mRNA levels, whereas it increased O(2)(-) levels. Antioxidant seleno-l-methionine; chemical inhibitors of p38, ERK1/2, and mitochondrial complex II; as well as dominant negative mutant forms of IkappaBalpha and NOX4 effectively blocked sCD40L-induced eNOS down-regulation in HCAECs. Thus, sCD40L reduces eNOS levels, whereas it increases oxidative stress through the unique molecular mechanisms involving eNOS mRNA stability, 3'UTR-binding molecules, microRNAs, mitochondrial function, ROS-related enzymes, p38, ERK1/2, and NF-kappaB signal pathways in endothelial cells.

Xenogeneic interaction between human CD40L and porcine CD40 activates porcine endothelial cells through NF-κB signaling

Xenotransplantation is a promising alternative to overcome donor shortage in transplantation. CD40 molecule plays an important role in the interaction of T cells with antigen-presenting cells and in the activation of vascular endothelial cells. We investigated whether the xenogeneic interaction between human CD40L (hCD40L) on T cells and porcine endothelial CD40 (pCD40) can activate porcine endothelial cells (PECs). The interaction between hCD40L and pCD40 induced the expression of chemokines on PECs as well as MHC and adhesion molecules. Furthermore, NF-kappaB signaling was activated in HEK 293 cells expressing pCD40 and PECs by stimulation with hCD40L+ Jurkat T clones. Both anti-CD40L neutralizing antibodies and NF-kappaB signal inhibitors interfered with immune activation of PECs. Overall, this study shows that xenogeneic interaction between hCD40L and pCD40 can activate PECs through NF-kappaB signaling, and therefore may contribute to acute vascular rejection in xenotransplantation.

TRAF proteins in CD40 signaling

The tumor necrosis factor receptor (TNFR) superfamily molecule CD40 is expressed by a wide variety of cell types following activation signals, and constitutively on B lymphocytes, macrophages, and dendritic cells. CD40 signals to cells stimulate kinase activation, gene expression, production of a antibody and a variety of cytokines, expression or upregulation of surface molecules, and protection or promotion of apoptosis. Initial steps in CD40-mediated signal cascades involve the interactions of CD40 with various members of the TNFR-associated factor (TRAF) family of cytoplasmic proteins. This review summarizes current understanding of the nature of these interactions, and how they induce and regulate CD40 functions.

Detection of HDM2 and VEGF co-expression in cancer cell lines: novel effect of HDM2 antisense treatment on VEGF expression

The human homologue of murine double minute 2 (HDM2) oncogene is amplified in approximately 7% of all human cancers. Overexpression of HDM2 protein impairs cell cycle control and confers growth advantage to cancer cells. In several cancers the progression of tumor growth and formation of distant metastases are found to be dependent on tumor angiogenesis, a process that is regulated by vascular endothelial growth factor (VEGF). In this study, we have investigated the co-expression of HDM2 and VEGF in various types of human cancer cell lines and have shown that the co-expression is not cell-type-specific. Furthermore, when different types of cell lines were treated with a HDM2 gene specific antisense phosphorothioate oligodeoxynucleotide (HDMAS5), the expression of VEGF mRNA as well as the levels of VEGF protein was found to be decreased. Interestingly, the higher basal levels of VEGF mRNA and the protein observed in HDM2 transfected LNCaP-MST cells were effectively suppressed by HDMAS5 treatment. On the contrary, the mutant oligodeoxynucleotide containing 4 mismatched bases (M4) did not alter the expression of either HDM2 or VEGF in any of the cell lines tested. In conclusion, our findings are the first time evidence showing that HDM2 and VEGF are co-expressed in various cancer cell lines that have aggressive growth and high metastatic abilities. Furthermore, the decrease in VEGF expression observed at the transcriptional as well as translational levels, subsequent to HDMAS5 treatment of p53 null cells, strongly suggests that HDM2 has a regulatory role on VEGF expression in a p53 independent manner.

Increased expression of inflammation-related co-stimulatory molecules by HUVECs from newborns with a strong family history of myocardial infarction stimulated with TNF-alpha and oxLDL

BACKGROUND

Recent findings indicate that atherosclerosis, a chronic inflammatory process, might start during childhood. Nevertheless, the expression of inflammation-related molecules of endothelial cell isolated from healthy neonates with a strong family history of myocardial infarction (SFHMI) has been rarely analyzed.

METHODS

Human umbilical vein endothelial cells (HUVECs) from children with SFHMI were assessed for the expression of CD40 and CD40L, in the presence of TNF-alpha and oxLDL. The intracellular content of CD80, CXCL8 and tissue factor by HUVECs stimulated with a CD40 agonist monoclonal antibody as well as monocytes/lymphocyte adhesion to TNF-alpha-stimulated HUVECs was also evaluated.

RESULTS

The basal expression of CD40 and CD40L was higher in SFHMI-positive HUVECs in comparison to controls. TNF-alpha and oxLDL upregulated the expression of CD40 and CD40L in SFHMI versus control HUVECs (p<0.001). The intracellular expression of CXCL8, tissue factor and CD80 was also higher than in controls, and the adhesion of lymphocyte- and monocyte-like cells augmented upon TNF-alpha stimulation.

CONCLUSIONS

It is possible that the modifications observed in the SFHMI-positive HUVECs, all of them relevant to the atherosclerosis process, may lead to early inflammatory reactions, thus contributing to the premature initiation of atherosclerotic lesions in these children.

The effects of mTOR-Akt interactions on anti-apoptotic signaling in vascular endothelial cells

Recent studies have determined that mTOR mediates the activation of the protein kinase Akt in several cell types, but little is known about the association between mTOR and Akt in vascular endothelial cells. Furthermore, the functional significance of mTOR/Akt signaling has not been characterized in the endothelium. In these studies we treated endothelial cells with the mTOR inhibitor rapamycin, and we found that it decreases Akt phosphorylation and activity, as determined by phosphorylation of its substrate glycogen synthase kinase-3. This effect of rapamycin on Akt phosphorylation could not be demonstrated in endothelial cells transfected with a rapamycin-resistant mTOR construct. Also, in the presence of rapamycin, vascular endothelial growth factor, tumor necrosis factor, and insulin failed to phosphorylate Akt, further indicating that mTOR regulates Akt activation in endothelial cells. The activation of Akt is well established to mediate pro-survival signals. In part this is mediated via the phosphorylation and inactivation of the pro-apoptotic Akt substrates Foxo1 and Foxo3a. We find that rapamycin totally blocks vascular endothelial growth factor and Akt-inducible phosophorylation of these transcription factors in endothelial cells. Furthermore, inhibition of Akt activity by rapamycin increased the number of endothelial cells undergoing apoptosis after serum withdrawal as well as after stimulation by vascular endothelial growth factor or tumor necrosis factor. Taken together these observations demonstrate first, that mTOR regulates the phosphorylation and activation of Akt in endothelial cells and, second, that a major effect of mTOR inhibition in endothelial cells is to suppress Akt-inducible pro-survival signals.

Giving blood: a new role for CD40 in tumorigenesis

CD40 was initially identified as a receptor expressed by B cells that is crucial for inducing an effective adaptive immune response. CD40 was subsequently shown to be expressed by endothelial cells and to promote angiogenesis. New data now show that in tumor-prone transgenic mice, CD40-mediated neovascularization is essential for early stage tumorigenicity. This suggests, at least in this mouse model, that CD40 has an important role in the angiogenic process that is coupled to carcinogenesis, a finding that could lead to novel therapeutic opportunities.

The role of phosphoinositide 3-kinase/Akt signaling in low-dose mercury-induced mouse pancreatic beta-cell dysfunction in vitro and in vivo

The relationship between oxidation stress and phosphoinositide 3-kinase (PI3K) signaling in pancreatic beta-cell dysfunction remains unclear. Mercury is a well-known toxic metal that induces oxidative stress. Submicromolar-concentration HgCl(2) or methylmercury triggered reactive oxygen species (ROS) production and decreased insulin secretion in beta-cell-derived HIT-T15 cells and isolated mouse islets. Mercury increased PI3K activity and its downstream effector Akt phosphorylation. Antioxidant N-acetyl-l-cysteine (NAC) prevented mercury-induced insulin secretion inhibition and Akt phosphorylation but not increased PI3K activity. Inhibition of PI3K/Akt activity with PI3K inhibitor or by expressing the dominant-negative p85 or Akt prevented mercury-induced insulin secretion inhibition but not ROS production. These results indicate that both PI3K and ROS independently regulated Akt signaling-related, mercury-induced insulin secretion inhibition. We next observed that 2- or 4-week oral exposure to low-dose mercury to mice significantly caused the decrease in plasma insulin and displayed the elevation of blood glucose and plasma lipid peroxidation and glucose intolerance. Akt phosphorylation was shown in islets isolated from mercury-exposed mice. NAC effectively antagonized mercury-induced responses. Mercury-induced in vivo effects and increased blood mercury were reversed after mercury exposure was terminated. These results demonstrate that low-dose mercury-induced oxidative stress and PI3K activation cause Akt signaling-related pancreatic beta-cell dysfunction.

Internalization of CD40 regulates its signal transduction in vascular endothelial cells

The CD40 ligand (CD40L)-CD40 dyad can ignite proinflammatory and procoagulatory activities of the vascular endothelium in the pathogenesis and progression of atherosclerosis. Besides being expressed on the activated CD4(+) T cell surface (mCD40L), the majority of circulating CD40L reservoir (sCD40L) in plasma is released from stimulated platelets. It remains debatable which form of CD40L triggers endothelial inflammation. Here, we demonstrate that the agonistic antibody of CD40 (G28.5), which mimics the action of sCD40L, induces rapid endocytosis of CD40 independent of TRAF2/3/6 binding while CD40L expressed on the surface of HEK293A cells captures CD40 at the cell conjunction. Forced internalization of CD40 by constitutively active mutant of Rab5 preemptively activates NF-kappaB pathway, suggesting that CD40 was able to form an intracellular signal complex in the early endosomes. Internalized CD40 exhibits different patterns of TRAF2/3/6 recruitment and Akt phosphorylation from the membrane anchored CD40 complex. Finally, mCD40L but not sCD40L induces the upregulation of proinflammatory cytokines and cell adhesion factors in the primary human vascular endothelial cells in vitro, although both forms of CD40L activate NF-kappaB pathway. These results therefore may help understand the molecular mechanism of CD40L signaling that contributes to the pathophysiology of atherosclerosis.

T cells and B cells in the pathogenesis of systemic sclerosis: recent insights and therapeutic opportunities

Among the earliest pathologic events in systemic sclerosis (SSc) is the infiltration of mononuclear cells into the skin lesion. This inflammatory cell infiltration precedes the development of fibrosis, suggesting an integral role for the presence of these cells in the fibrotic events observed in the lesion. However, immunosuppressive therapies that are effective in other autoimmune disease have not been successful in the treatment of SSc, making the clinical management of this disease very difficult. The aim of this paper is to review the latest findings regarding the activation and the functional polarization of T cells and their role in the pathogenesis of SSc. Furthermore, the potential role of B cells, a hitherto scantily investigated inflammatory cell in SSc, is discussed. Understanding the interplay between T and B cells, and the processes that promote the fibrotic cytokine pattern seen in these patients is of utmost importance for the development of effective therapies to treat the clinical complications.

Vascular endothelial growth factor-induced signaling pathways in endothelial cells that mediate overexpression of the chemokine IFN-gamma-inducible protein of 10 kDa in vitro and in vivo

Vascular endothelial growth factor (VEGF), an angiogenesis factor, has recently been found to have potent proinflammatory properties in vivo. However, the mechanism by which it mediates inflammation is poorly understood. In this study, we have evaluated the function of VEGF on the induced expression and function of the T cell chemoattractant chemokine IFN-gamma-inducible protein of 10 kDa (IP-10). In vitro, we find that VEGF augments the effect of IFN-gamma on the induction of IP-10 mRNA and protein expression in endothelial cells. Moreover, we show that VEGF and IFN-gamma regulate the activation of the IP-10 promoter, and that the kinases PI3K, phosphoinositide-dependent kinase 1, and Akt act as intermediary signaling molecules for cytokine-inducible IP-10 transcriptional activation in endothelial cells. To examine whether VEGF is functional for IP-10 expression in vivo, Chinese hamster ovary cells that were designed to secrete VEGF were injected s.c. into the skin of nude mice and were found to mediate a time-dependent increase in IP-10 mRNA. This response was reduced in animals treated systemically with the PI3K inhibitor wortmannin. When the Chinese hamster ovary cells expressing VEGF plasmid were injected s.c. into C57BL/6 wild-type or CXCR3-/- mice, they elicited an inflammatory reaction in wild-type but not in CXCR3-/- mice. Collectively, these findings indicate that VEGF-induced augmentation of IP-10 expression is a major mechanism underlying its proinflammatory function.

Atherosclerotic plaque progression and vulnerability to rupture: angiogenesis as a source of intraplaque hemorrhage

Observational studies of necrotic core progression identify intraplaque hemorrhage as a critical factor in atherosclerotic plaque growth and destabilization. The rapid accumulation of erythrocyte membranes causes an abrupt change in plaque substrate characterized by increased free cholesterol within the lipid core and excessive macrophage infiltration. Neoangiogenesis is associated closely with plaque progression, and microvascular incompetence is a likely source of intraplaque hemorrhage. Intimal neovascularization is predominantly thought to arise from the adventitia, where there are a plethora of pre-existing vasa vasorum. In lesions that have early necrotic cores, the majority of vessels invading from the adventitia occur at specific sites of medial wall disruption. A breech in the medial wall likely facilitates the rapid in-growth of microvessels from the adventitia, and exposure to an atherosclerotic environment stimulates abnormal vascular development characterized by disorganized branching and immature endothelial tubes with "leaky" imperfect linings. This network of immature blood vessels is a viable source of intraplaque hemorrhage providing erythrocyte-derived phospholipids and free cholesterol. The rapid change in plaque substrate caused by the excessive accumulation of erythrocytes may promote the transition from a stable to an unstable lesion. This review discusses the potential role of intraplaque vasa vasorum in lesion instability as it relates to plaque rupture.

CD40: A Mediator of Pro- and Anti-Inflammatory Signals in Renal Tubular Epithelial Cells

Infiltration of immune cells into the renal interstitium is characteristic of chronic inflammatory kidney diseases. CD4+ T cells and platelets express CD40 ligand (CD40L) and are reported to mediate proinflammatory events in renal proximal tubular epithelial cells (RPTEC) via interaction with CD40. In other cell types, CD40 signals can also induce protective genes. Here, human RPTEC were treated with sCD40L to ligate CD40, and a significant increase in the generation of proinflammatory reactive oxygen species was found; however, CD40-activated cells did not undergo apoptosis. This suggests that CD40 signals may simultaneously induce antiapoptotic genes for cytoprotection of RPTEC. Heme oxygenase-1 (HO-1) expressed in RPTEC serves as a protective gene, but it is not known whether it is regulated by CD40. Next, RPTEC were transiently transfected with a full-length HO-1 promoter-luciferase construct and were treated with sCD40L. CD40 ligation was found to significantly increase HO-1 promoter activity. By electrophoretic mobility shift assay, it was confirmed that CD40 signaling induced the transcriptional activation of HO-1 through the binding of NF-kappaB to its promoter. By Western blot analysis, a marked increase in HO-1 protein expression following CD40 ligation was also found. These observations are of clinical significance because it was found that CD40 and HO-1 are induced in expression in vivo in inflamed rejecting kidney biopsies and co-expressed in renal tubules. Therefore, ligation of CD40 in RPTEC promotes both inflammatory and anti-inflammatory processes. Regulating the balance between these two events may be of importance in the prevention of tubular injury associated with renal disease.

CD40/CD154 ligation induces mononuclear cell adhesion to human renal proximal tubule cells via increased ICAM-1 expression

The role of CD40/CD154 ligation in the upregulation of genes of the proinflammatory nuclear factor-κB (NF-κB) signal transduction pathway was explored in primary cultures of human renal proximal tubule epithelial cells. Using a cDNA gene array specific for human NF-κB signal pathway genes, 38 genes were upregulated at 1 h, and 7 of these genes remained upregulated at 3 h. Of these genes, intercellular adhesion molecule-1 (ICAM-1) was explored in further detail. Quantitative real-time PCR for ICAM-1 mRNA expression confirmed the gene array findings. Western blot analysis and quantitative sandwich-enzyme ELISA confirmed this observation at the protein level. A cell-surface ELISA assay showed that ICAM-1 expression doubled by 48 h of CD154 exposure, and fluorescence-activated cell sorter analysis suggested that both the number of cells expressing ICAM-1 and the expression of ICAM-1 on these cells had increased. A cell adhesion assay using fluorescein-labeled human peripheral mononuclear cells showed that ICAM-1 upregulation resulted in increased mononuclear cell adhesion to the monolayer, which was abrogated by pretreatment of the monolayer with a neutralizing ICAM-1 antibody. The p38 mitogen-activated protein kinase (MAPK) inhibitor SB-203580 but not the extracellular signal-regulated kinase 1/2 inhibitor (PD-98059) nor the protein kinase C inhibitor (calphostin) blunted ICAM-1 expression and mononuclear cell adhesion to the monolayer. We conclude that, in human renal proximal tubule epithelial cells, CD40 activation upregulates ICAM-1 (and other NF-κB pathway genes) expression with concomitant enhanced adhesion of mononuclear cells, which is mediated via the p38 MAPK signal transduction pathway.

Raf and VEGF: emerging therapeutic targets in Kaposi's sarcoma-associated herpesvirus infection and angiogenesis in hematopoietic and nonhematopoietic tumors

Kaposi's sarcoma-associated herpesvirus (KSHV) is etiologically associated with several cancers including Kaposi's sarcoma (KS), primary effusion lymphoma, and multicentric Castleman's disease. KSHV-mediated pathogenesis is dependent mainly on KSHV infection as well as on the microenvironment provided by the growth factors (GFs)/inflammatory cytokines (ICs). Recently, we determined that oncoprotein Raf enhances KSHV infection of target cells. Interestingly, Raf regulates the expression of a variety of GFs/ICs including those involved in angiogenesis such as vascular endothelial growth factor (VEGF). In this review, we discuss the effect of the Raf-GF/IC autocrine/paracrine loop on KSHV infection of both hematopoietic and nonhematopietic cells, and associated disease conditions.