Human mesangial cells and peripheral blood mononuclear cells produce vascular permeability factor

Effects of Hyperglycemia on Angiogenesis in Human Placental Endothelial Cells

The placenta is a temporary organ that provides communication between the mother and fetus. Maternal diabetes and abnormal placental angiogenesis may be linked. We investigated the angiogenesis mechanism resulting from VEGF and glucose stimulation in PECs obtained from human term placenta. Immunohistochemistry was performed to characterize PECs obtained from human term placenta. D-glucose was added to the medium containing PECs to establish normoglycemic and hyperglycemic conditions. The expression levels of VEGF, VEGFR-1 and VEGFR-2 genes and proteins in PECs from the control and experimental groups were analyzed by RT-PCR and Western blotting, respectively. With 48-hours incubation, gene expressions increased due to hyperglycemia, while protein levels increased due to the combined effect of VEGF and hyperglycemia. While VEGFR-2 gene expression and protein amounts increased in 24-hours due to the combined effect of VEGF and hyperglycemia, the effect of VEGF stimulation and glucose level on VEGFR-2 decreased in 48-hour incubation with time. VEGF, VEGFR-1 and VEGFR-2 genes and proteins were affected by hyperglycemic conditions in PECs. Hyperglycemia occurring in various conditions such as gestational diabetes mellitus and diabetes mellitus may affect VEGF, VEGFR-1 and VEGFR-2 genes and proteins of PECs derived from human term placenta.

Intricate role of sleep deprivation in modulating depression: focusing on BDNF, VEGF, serotonin, cortisol, and TNF-α

In this review article, we aimed to discuss intricate roles of SD in modulating depression in preclinical and clinical studies. Decades of research have shown the inconsistent effects of SD on depression, focusing on SD duration. However, inconsistent role of SD seems to be more complicated, and SD duration cannot be the only one factor. Regarding this issue, we chose some important factors involved in the effects of SD on cognitive functions and mood including brain-derived neurotrophic factor (BDNF), vascular endothelial growth factor (VEGF), serotonin, cortisol, and tumor necrosis factor-alpha (TNF-α). It was concluded that SD has a wide-range of inconsistent effects on BDNF, VEGF, serotonin, and cortisol levels. It was noted that BDNF diurnal rhythm is significantly involved in the modulatory role of SD in depression. Furthermore, the important role of VEGF in blood-brain barrier permeability which is involved in modulating depression was discussed. It was also noted that there is a negative correlation between cortisol and BDNF that modulates depression. Eventually, it was concluded that TNF-α regulates sleep/wake cycle and is involved in the vulnerability to cognitive and behavioral impairments following SD. TNF-α also increases the permeability of the blood-brain barrier which is accompanied by depressive behavior. In sum, it was suggested that future studies should focus on these mechanisms/factors to better investigate the reasons behind intricate roles of SD in modulating depression.

Interleukin-37, vascular endothelial growth factor A, and transforming growth factor-β1: promising biomarkers in primary immune thrombocytopenia

BACKGROUND

Immune thrombocytopenic purpura (ITP) is an acquired autoimmune hematologic disorder with heterogeneous bleeding manifestations. Many biomarkers such as interleukin-37 (IL-37), vascular endothelial growth factor A (VEGFA), and transforming growth factor-β1 (TGFß1) have a role in immunity, inflammation, and megakaryopoiesis.

METHODS

In the present study, immunoassay of interleukin-37 as well as the gene expression of vascular endothelial growth factor A and transforming growth factor-β1 were done in 60 primary ITP patients, 60 thrombocytopenia patients, and 60 healthy volunteers.

RESULTS

Increased IL-37 level and down regulation of VEGFA and TGFß1gene expression were detected in primary ITP patients when compared with other groups. A negative correlation was observed between IL-37 and platelet count. However, a positive correlation was observed between VEGFA and TGFß1 levels and platelet count.

CONCLUSION

Current results suggested that interleukin-37, vascular endothelial growth factor A, and transforming growth factor-β may be promising indicators in the diagnosis of ITP and detection of disease severity with inexpensive and cost-effectiveness compared to the benefits.

Receptor, Signal, Nucleus, Action: Signals That Pass through Akt on the Road to Head and Neck Cancer Cell Migration

Simple Summary

The ecosystem that surrounds a tumour, the microenvironment, has a huge impact on the spread of cancer, but its exact role in the molecular mechanism of spreading is still under scrutiny. This literature review aims to focus on the evidence published on the production of growth factors or proteins from the tumour microenvironment, which initiate signals in cancer cells. This review provides evidence that when Akt, a signalling protein, is activated by different growth factors such as epidermal growth factor, transforming growth factor α/β, vascular endothelial growth factor and nerve growth factor, head and neck cancer cell spreading is stimulated. In a nutshell, it demonstrates that the tumour microenvironment plays an important role in cancer spreading by synthesising and secreting growth factors and suggests that targeting growth-factor-activated Akt in combination therapy could be a valuable therapeutic approach in treating head and neck cancer patients.

Abstract

This review aims to provide evidence for the role of the tumour microenvironment in cancer progression, including invasion and metastasis. The tumour microenvironment is complex and consists of tumour cells and stromal-derived cells, in addition to a modified extracellular matrix. The cellular components synthesise growth factors such as EGF, TGFα and β, VEGF, and NGF, which have been shown to initiate paracrine signalling in head and neck cancer cells by binding to cell surface receptors. One example is the phosphorylation, and hence activation, of the signalling protein Akt, which can ultimately induce oral cancer cell migration in vitro. Blocking of Akt activation by an inhibitor, MK2206, leads to a significant decrease, in vitro, of cancer-derived cell migration, visualised in both wound healing and scatter assays. Signalling pathways have therefore been popular targets for the design of chemotherapeutic agents, but drug resistance has been observed and is related to direct tumour–tumour cell communication, the tumour–extracellular matrix interface, and tumour–stromal cell interactions. Translation of this knowledge to patient care is reliant upon a comprehensive understanding of the complex relationships present in the tumour microenvironment and could ultimately lead to the design of efficacious treatment regimens such as targeted therapy or novel therapeutic combinations.

Anti-Angiogenic and Cytotoxicity Effects of Selachyl Alcohol Analogues

BACKGROUND

The active ingredients in the shark liver oil (SLO) mixture were found to be a group of etherlinked glycerol known as alkylglycerols (AKGs). During the last century, initial clinical use of the SLO mixture was for treating leukemias and later preventing radiation sickness from cancer x-ray therapy. Selachyl alcohol is one of the most abundant AKGs in the SLO mixture and it displayed strong activity in reducing lung metastasis number on a model of grafted tumor in mice (Lewis lung carcinoma cells).

OBJECTIVES

In this study, selachyl alcohol analogue containing methoxyl (7), gem-difluorinated (8), azide (9) and hydroxyl (10) group at the 12 position in the alkyl chain were synthesized and compared regarding their cytotoxicity and anti-migratory effects on Human Umbilical Vein Endothelial Cell line.

METHODS

AKGs 7-10 were synthesized according to the literature procedure. The cytotoxicity of the studied AKGs was evaluated by the MTT test and Human Umbilical Vein Endothelial Cell line (HUVEC) was used as an in vitro model to evaluate their anti-migratory effects.

RESULTS

The four AKGs have substantially the same toxicity threshold (≥ 12 μM), whereas they have an anti-migratory activity significantly different on endothelial cells. AKGs 9 and 10 significantly reduce the chemotactic migration induced by VEGF, but analogue (10) containing the hydroxyl group at the 12 position in the alkyl chain was the most potent anti-VEGF inhibitor.

CONCLUSION

We presented here a series of four synthetic selachyl alcohol analogues, among which AKGs 9 and 10 showed the ability to inhibit endothelial cell migration. The relationship structures and anti-VEGF effects of these analogues were also evaluated and discussed. Unnatural synthesized AKGs could be explored as one new source of anticancer agents.

The transcription factor C/EBPβ promotes vascular endothelial growth factor A expression and neural stem cell expansion

The bZIP transcription factor CCAAT enhancer-binding protein β (C/EBPβ) exhibits neurogenic, neuritogenic, and pro-survival effects in the central nervous system. Here, we show that C/EBPβ regulates neural stem cell (NSC) expansion and vascular endothelial growth factor A (VEGF-A) level by acting on a C/EBPβ-responsive element within the Vegf-a promoter. As predicted, C/EBPβ depletion reduced VEGF-A production, NSC number, and average neurosphere size in proliferating cultures. Conversely, deletion of the C/EBPβ repressor CHOP-10 induced C/EBPβ and VEGF-A expression, while stimulating NSC expansion. These data highlight the role of C/EBPβ in regulating VEGF-A production and the growth of NSCs and suggest CHOP-dependent antagonism of C/EBPβ may function as a transcriptional rheostat linking stress-associated cues with stem cell quiescence among other pathological responses affecting the neurogenic niche.

Rac Signaling Drives Clear Cell Renal Carcinoma Tumor Growth by Priming the Tumor Microenvironment for an Angiogenic Switch

Clear cell renal cell carcinoma (ccRCC) remains a common cause of cancer mortality. Better understanding of ccRCC molecular drivers resulted in the development of antiangiogenic therapies that block the blood vessels that supply tumors with nutrients for growth and metastasis. Unfortunately, most ccRCC patients eventually become resistant to initial treatments, creating a need for alternative treatment options. We investigated the role of the small GTPase Rac1 in ccRCC. Analysis of ccRCC clinical samples indicates that Rac signaling drives disease progression and predicts patients with poorer outcomes. Investigation of Rac1 identifies multiple roles for Rac1 in the pathogenesis of ccRCC. Rac1 is overexpressed in RCC cell lines and drives proliferation and migratory/metastatic potential. Rac1 is also critical for endothelial cells to grow and form endothelial tubular networks potentiated by angiogenic factors. Importantly, Rac1 controls paracrine signaling of angiogenic factors including VEGF from renal carcinoma cells to surrounding blood vessels. A novel Rac1 inhibitor impaired the growth and migratory potential of both renal carcinoma cells and endothelial cells and reduced VEGF production by RCC cells, thereby limiting paracrine signaling both in vitro and in vivo Lastly, Rac1 was shown to be downstream of VEGF receptor (VEGFR) signaling and required for activation of MAPK signaling. In combination with VEGFR2 inhibitors, Rac inhibition provides enhanced suppression of angiogenesis. Therefore, targeting Rac in ccRCC has the potential to block the growth of tumor cells, endothelial cell recruitment, and paracrine signaling from tumor cells to other cells in the tumor microenvironment.

Vascular endothelial growth factor (VEGF-A) and fibroblast growth factor (FGF-2) as potential regulators of seasonal reproductive processes in male European bison (Bison bonasus, Linnaeus 1758)

Growth factors: vascular endothelial growth factor A (VEGF-A) and fibroblast growth factor (FGF-2) were reported to affect normal physiological reproductive processes in human, domestic and free living animals. Moreover, some reports suggest that VEGF-A and FGF-2 may be directly involved in the control of the annual reproductive cycle of seasonally breeding animals but detailed knowledge is still missing. Our study aimed to demonstrate the expression of mRNA and protein for both factors in the tissues of testis and epididymis (caput, corpus, cauda) at different periods of the year (March, June, November, December) in European bison as a model of seasonally breeding animal. Results suggest, that VEGF-A expression was more pronounced in testis than in epididymis and the highest expression was noted in December and June. Surprisingly, the highest protein accumulation was observed in June at the same level in all tissues analyzed. On the other hand, the highest FGF-2 mRNA expression was noted in testis in June and in epididymis in March. However, no differences in protein expression of FGF-2 were found between analyzed groups. The results indicate that both factors are necessary for proper functioning of the reproductive system and their levels differ seasonally. Perhaps, it is linked to increased need of these factors in the testis as well as epididymis during preparation for the reproductive functions. Moreover, VEGF-A and FGF-2 not only may regulate reproductive functions by affecting vascularization and cell nutrition, but it also may be possible that they possess protective functions by stabilizing the reproductive cells. Therefore, obtained results provide new insight into mechanisms underlying seasonal breeding of the male European bison.

Chronic cocaine induces HIF-VEGF pathway activation along with angiogenesis in the brain

Cocaine induces vasoconstriction in cerebral vessels, which with repeated use can result in transient ischemic attacks and cerebral strokes. However, the neuroadaptations that follow cocaine's vasoconstricting effects are not well understood. Here, we investigated the effects of chronic cocaine exposure (2 and 4 weeks) on markers of vascular function and morphology in the rat brain. For this purpose we measured nitric oxide (NO) concentration in plasma, brain neuronal nitric oxide synthase (nNOS or NOS1), HIF-1α, and VEGF expression in different brain regions, i.e., middle prefrontal cortex, somatosensory cortex, nucleus accumbens, and dorsal striatum, using ELISA or Western blot. Additionally, microvascular density in these brain regions was measured using immunofluorescence microscopy. We showed that chronic cocaine significantly affected NOS1, HIF-1α and VEGF expression, in a region- and cocaine treatment-time- dependent manner. Cerebral microvascular density increased significantly in parallel to these neurochemical changes. Furthermore, significant correlations were detected between VEGF expression and microvascular density in cortical regions (middle prefrontal cortex and somatosensory cortex), but not in striatal regions (nucleus accumbens and dorsal striatum). These results suggest that following chronic cocaine use, as cerebral ischemia developed, NOS1, the regulatory protein to counteract blood vessel constriction, was upregulated; meanwhile, the HIF-VEGF pathway was activated to increase microvascular density (i.e., angiogenesis) and thus restore local blood flow and oxygen supply. These physiological responses were triggered presumably as an adaptation to minimize ischemic injury caused by cocaine. Therefore, effectively promoting such physiological responses may provide novel and effective therapeutic solutions to treat cocaine-induced cerebral ischemia and stroke.

Diabetes-Induced Reactive Oxygen Species: Mechanism of Their Generation and Role in Renal Injury

Diabetes induces the onset and progression of renal injury through causing hemodynamic dysregulation along with abnormal morphological and functional nephron changes. The most important event that precedes renal injury is an increase in permeability of plasma proteins such as albumin through a damaged glomerular filtration barrier resulting in excessive urinary albumin excretion (UAE). Moreover, once enhanced UAE begins, it may advance renal injury from progression of abnormal renal hemodynamics, increased glomerular basement membrane (GBM) thickness, mesangial expansion, extracellular matrix accumulation, and glomerulosclerosis to eventual end-stage renal damage. Interestingly, all these pathological changes are predominantly driven by diabetes-induced reactive oxygen species (ROS) and abnormal downstream signaling molecules. In diabetic kidney, NADPH oxidase (enzymatic) and mitochondrial electron transport chain (nonenzymatic) are the prominent sources of ROS, which are believed to cause the onset of albuminuria followed by progression to renal damage through podocyte depletion. Chronic hyperglycemia and consequent ROS production can trigger abnormal signaling pathways involving diverse signaling mediators such as transcription factors, inflammatory cytokines, chemokines, and vasoactive substances. Persistently, increased expression and activation of these signaling molecules contribute to the irreversible functional and structural changes in the kidney resulting in critically decreased glomerular filtration rate leading to eventual renal failure.

Therapeutic angiogenesis by vascular endothelial growth factor supplementation for treatment of renal disease

PURPOSE OF REVIEW

Vascular endothelial growth factors (VEGFs) influence renal function through angiogenesis, with VEGF-A being the most potent inducer of vascular formation. In the normal glomerulus, tight homeostatic balance is maintained between the levels of VEGF-A isoforms produced by podocyte cells, and the VEGF receptors (VEGFRs) expressed by glomerular endothelial, mesangial, and podocyte cells. Renal disease occurs when this homeostatic balance is lost, manifesting in the abnormal autocrine and paracrine VEGF-A/VEGFR signaling, ultrastructural glomerular and tubular damage, and impaired filtration.

RECENT FINDINGS

Preclinical disease models of ischemic renal injury, including acute ischemia/reperfusion, thrombotic microangiopathy, and chronic renovascular disease, treated with exogenous VEGF supplementation demonstrated therapeutic efficacy. These results suggest a therapeutic VEGF-A paracrine effect on endothelial cells in the context of acute or chronic obstructive ischemia. Conversely, renal dysfunction in diabetic nephropathy appears to occur through an upregulated VEGF autocrine effect on podocyte cells, which is exacerbated by hyperglycemia. Therefore, VEGF supplementation therapy may be contraindicated for treatment of diabetic nephropathy, but specific results will depend on dose and on the specific site of VEGF delivery. A drug delivery system that demonstrates cell specificity for glomerular or peritubular capillaries could be employed to restore balance to VEGF-A/VEGFR2 signaling, and by doing so, prevent the progression to end-stage renal disease.

SUMMARY

The review discusses the preclinical data available for VEGF supplementation therapy in models of renal disease.

Platelet-Rich Plasma in a Murine Model: Leukocytes, Growth Factors, Flt-1, and Muscle Healing

BACKGROUND

It is well known that platelet-rich plasma (PRP) preparations are not the same and that not all preparations include white blood cells, but the part that leukocytes play on the healing role of PRP is still unknown.

PURPOSE

The primary aim of this study was to evaluate the influence of leukocytes in different PRP preparations with a special emphasis on growth factor concentrations. The secondary aim was to evaluate the influence of PRP on muscle healing.

STUDY DESIGN

Controlled laboratory study.

METHODS

Two PRP preparation procedures were evaluated. Blood fractions were stained with Rapid Panoptic, and growth factors (transforming growth factor beta 1 [TGF-β1], vascular endothelial growth factor [VEGF], insulin-like growth factor [IGF], epidermal growth factor [EGF], hepatocyte growth factor [HGF], and platelet-derived growth factor [PDGF]) were quantified by enzyme-linked immunosorbent assay. Western blotting analysis was performed for Fms-related tyrosine kinase 1 (Flt-1). A muscle contusion injury was created and treated with PRP at different time points.

RESULTS

Leukocytes were the main source of VEGF, and all other growth factors measured had a higher concentration in the preparations that included the buffy coat and consequently had a higher concentration of white blood cells. Flt-1 was also found in platelet-poor plasma (PPP). There were higher concentrations of PDGF and HGF in the preparations that encompassed the buffy coat. A PRP injection 7 days after the injury provided significantly increased exercise performance and decreased the fibrotic area when compared with other PRP-treated groups.

CONCLUSION

VEGF is only present in PRP's buffy coat, while Flt-1 is present in PPP. A PRP injection 7 days after an injury resulted in improved exercise performance.

CLINICAL RELEVANCE

The presence of Flt-1 in PRP provides yet another explanation for results described in the literature after a PRP injection. This information is relevant for selecting the best PRP for each type of injury.

Involvement of vascular endothelial growth factor -460 C/T, +405 G/C and +936 C/T polymorphisms in the development of endometriosis

There are inconsistent data on the contribution of vascular endothelial growth factor (VEGF) -460 C/T (rs833061), +405 G/C (rs2010963) and +936 C/T (rs3025039) single-nucleotide polymorphisms (SNPs) to endometriosis in different ethnicities. Therefore, using high-resolution melting curve analysis, the present study examined the distribution of these SNPs in females with endometriosis-related infertility and a control group. None of the three VEGF SNPs were associated with endometriosis-related infertility in the dominant and recessive models. The lowest P-values of the trend were observed for the VEGF +936 C/T (rs3025039) SNP in endometriosis-related infertility (P_trend =0.149). Similarly, haplotype analyses of VEGF SNPs did not demonstrate any SNP combination as a risk for endometriosis-related infertility, and the lowest overall P-values, P=0.141 and P_corr =0.395, were observed for a haplotype (TGT) of the above SNPs. Taken together, these results did not demonstrate the contribution of VEGF C/T, +405 G/C and +936 C/T SNPs to endometriosis-related infertility.

Calreticulin transacetylase mediated upregulation of thioredoxin by 7,8-diacetoxy-4-methylcoumarin enhances the antioxidant potential and the expression of vascular endothelial growth factor in peripheral blood mononuclear cells

Extensive research carried out in our group on polyphenolic acetates (PAs) substantiated the potential role of PAs in causing diverse biological and pharmacological actions. Our earlier investigations firmly established the calreticulin transacetylase (CRTAase) catalyzed activation of nitric oxide synthase (NOS) by PAs. In this report, we have studied the effect of 7,8-diacetoxy-4-methylcoumarin (DAMC, a model PA) and other acetoxy coumarins on the thioredoxin and VEGF expression in human peripheral blood mononuclear cells (PBMCs), with a view to substantiate our earlier observation that DAMC was a superb inducer of angiogenesis. Real time RT-PCR analysis revealed the enhanced expression of thioredoxin reductase (TRXR) and diminished expression of thioredoxin interacting protein (TRXIP) leading to the increased expression and activity of thioredoxin (TRX) in PBMCs due to the the action of DAMC. The fact that TRX activity of PBMCs was enhanced by various acetoxy coumarins in tune with their affinity to CRTAase as substrate, suggested the possible activation of TRX due to acetylation. The overexpression of thioredoxin was found to correlate with that of VEGF as proved by real time RT-PCR and VEGF -ELISA results, apart from the DAMC-caused enhanced production of NO acting as an inducer of VEGF. Moreover, the intracellular ROS levels were also found to be reduced drastically, by DAMC thus reducing the oxidative stress in cells. These observations strongly evidenced the crucial role of TRX in DAMC-induced tissue angiogenesis with the involvement of VEGF.

Quercetin-4'-O-β-D-glucopyranoside (QODG) inhibits angiogenesis by suppressing VEGFR2-mediated signaling in zebrafish and endothelial cells

BACKGROUND

Angiogenesis plays an important role in many physiological and pathological processes. Identification of small molecules that block angiogenesis and are safe and affordable has been a challenge in drug development. Hypericum attenuatum Choisy is a Chinese herb medicine commonly used for treating hemorrhagic diseases. The present study investigates the anti-angiogenic effects of quercetin-4'-O-β-D-glucopyranoside (QODG), a flavonoid isolated from Hypericum attenuatum Choisy, in vivo and in vitro, and clarifies the underlying mechanism of the activity.

METHODOLOGY/PRINCIPAL FINDINGS

Tg(fli1:EGFP) transgenic zebrafish embryos were treated with different concentrations of quercetin-4'-O-β-D-glucopyranoside (QODG) (20, 60, 180 µM) from 6 hours post fertilisation (hpf) to 72 hpf, and adult zebrafish were allowed to recover in different concentrations of QODG (20, 60, 180 µM) for 7 days post amputation (dpa) prior morphological observation and angiogenesis phenotypes assessment. Human umbilical vein endothelial cells (HUVECs) were treated with or without VEGF and different concentrations of QODG (5, 20, 60, 180 µM), then tested for cell viability, cell migration, tube formation and apoptosis. The role of VEGFR2-mediated signaling pathway in QODG-inhibited angiogenesis was evaluated using quantitative real-time PCR (qRT-PCR) and Western blotting.

CONCLUSION/SIGNIFICANCE

Quercetin-4'-O-β-D-glucopyranoside (QODG) was shown to inhibit angiogenesis in human umbilical vein endothelial cells (HUVECs) in vitro and zebrafish in vivo via suppressing VEGF-induced phosphorylation of VEGFR2. Our results further indicate that QODG inhibits angiogenesis via inhibition of VEGFR2-mediated signaling with the involvement of some key kinases such as c-Src, FAK, ERK, AKT, mTOR and S6K and induction of apoptosis. Together, this study reveals, for the first time, that QODG acts as a potent VEGFR2 kinase inhibitor, and exerts the anti-angiogenic activity at least in part through VEGFR2-mediated signaling pathway.

Impact of short-term systemic hypoxia on phagocytosis, cytokine production, and transcription factor activation in peripheral blood cells

Hypoxia frequently associated with certain physiologic and pathologic conditions influences numerous cellular functions. Because the effects of short-term hypoxia are incompletely understood, we examined phagocytosis and cytokine production as well as the activation of the transcription factors HIF-1 and NFκB in peripheral blood cells of healthy volunteers exposed to an oxygen concentration equivalent to that found at a height of 5500 m. Furthermore, we analysed plasma HIF-1 and serum concentrations of various HIF-1-dependent genes. Results showed that short-term hypoxia increased phagocytosis in neutrophils without affecting monocyte phagocytosis. Hypoxia decreased basal TNFα concentration in monocytes and basal interferon γ concentration in CD4(+) T lymphocytes. In contrast, plasma HIF and serum VEGF concentrations were not affected by hypoxia, although serum EPO concentration was raised. In PBMC, hypoxia increased cytosolic HIF-1 concentration without affecting nuclear HIF-1 concentration and led to a rise in the nuclear NFκB in PBMC. Our results show that short-term hypoxia affects immune functions in healthy individuals. Furthermore, we speculate that the effects of hypoxia are not due to HIF-1, but are caused by the activation of NFκB .

The role of vascular endothelial growth factor +405 G/C polymorphism and albuminuria in patients with type 2 diabetes mellitus

Observations on the association between the vascular endothelial growth factor (VEGF) gene polymorphism and nephropathy have been inconsistent, which might be due to ethnic and geographical variations. Furthermore, the relationship between +405 G/C polymorphism and albuminuria in the diabetic population has not been sufficiently studied. The aim of this study was to evaluate for the first time the possible association between +405 G/C polymorphism and albuminuria in an population from Tehran of Iran. A total of 255 consecutive patients with type 2 diabetes and microalbuminuria (Group A) and 235 patients with type 2 diabetes and normoalbuminuria (Group B) were included. Polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) were used to detect the VEGF alleles. In univariate analysis, the groups were statistically similar in all variables except for HbA1c (8.53 ± 1.7 in Group A vs. 8.2 ± 1.73 in Group B; P = 0.034), 24-h urinary albumin (201.33 ± 84.8 in Group A vs. 22.88 ± 3.5 in Group B; P < 0.001), and the frequency of GG genotype (31% in Group A vs. 18.7% in Group B; P = 0.006). The GG genotype was the independent predictor of albuminuria [P = 0.014, OR = 1.771, 95% confidence interval (CI) = 1.124-2.790]. Our study showed that the G allele was not associated with albuminuria, but the GG genotype in the VEGF gene is independently associated with development of nephropathy in the our diabetic population.

Vasopressin induces human mesangial cell growth via induction of vascular endothelial growth factor secretion

Vasoactive hormones, growth factors, and cytokines are important in promoting mesangial cell growth, a characteristic feature of many glomerular diseases. Vascular endothelial growth factor (VEGF) is an endothelial mitogen and promoter of vascular permeability that is constitutively expressed in human glomeruli, but its role in the kidney is still unclear. In the present study, we investigated the ability of vasopressin (AVP) to stimulate VEGF secretion by and correlation with AVP-induced cell growth in human mesangial cells. AVP caused time- and concentration-dependent increases in VEGF secretion from human mesangial cells, which was in turn potently inhibited by a V(1A) receptor-selective antagonist, confirming that this secretion is a V(1A) receptor-mediated event. VEGF also induced mesangial cell growth which was completely inhibited on administration of an anti-VEGF neutralizing antibody. Further, AVP-induced mesangial cell growth was completely abolished by the V(1A) receptor-selective antagonist and partially inhibited by an anti-VEGF neutralizing antibody. These results suggest that AVP stimulates VEGF secretion by human mesangial cells via V(1A) receptors. This secreted VEGF may function as an autocrine hormone to regulate mesangial cell growth, a mechanism by which AVP might contribute to progressive glomerular diseases such as diabetic nephropathy.

Vasopressin regulates rat mesangial cell growth by inducing autocrine secretion of vascular endothelial growth factor

Mesangial cell growth is a key feature of several glomerular diseases. Vascular endothelial growth factor (VEGF) is a potent mitogen of vascular endothelial cells and promoter of vascular permeability. Here, we examined the ability of vasopressin (AVP), which causes mesangial cell proliferation and hypertrophy, to stimulate VEGF secretion from cultured rat mesangial cells. AVP potently induced a time- and concentration-dependent increase in VEGF secretion in these cells, which was then inhibited by a V(1A) receptor-selective antagonist, confirming this is a V(1A) receptor-mediated event. VEGF also induced hyperplasia and hypertrophy in mesangial cells, which was completely abolished by an anti-VEGF antibody. In addition, AVP-induced hyperplasia and hypertrophy were completely inhibited by the V(1A) receptor-selective antagonist and partially abolished by the anti-VEGF antibody. These results indicate that AVP increases VEGF secretion in rat mesangial cells via V(1A) receptors and modulates mesangial cell growth not only by direct action but also through stimulation of VEGF secretion. This autocrine mechanism might contribute to glomerulosclerosis in renal diseases such as diabetic nephropathy.

Angiogenesis and chronic kidney disease

The number of patients requiring renal replacement therapy due to end-stage renal disease (ESRD) is increasing worldwide. The prevalence of chronic kidney disease (CKD), and the importance of CKD as a risk factor in development of ESRD and in complicating cardiovascular disease (CVD) have been confirmed. In recent years, the involvement of angiogenesis-related factors in the progression of CKD has been studied, and the potential therapeutic effects on CKD of modulating these factors have been identified. Vascular endothelial growth factor (VEGF)-A, a potent pro-angiogenic factor, is involved in the development of the kidney, in maintenance of the glomerular capillary structure and filtration barrier, and in the renal repair process after injury. VEGF-A is also involved in the development of early diabetic nephropathy, demonstrated by the therapeutic effects of anti-VEGF-A antibody. Angiopoietin (Ang)-1 induces the maturation of newly formed blood vessels, and the therapeutic effects of Ang-1 in diabetic nephropathy have been described. In experimental models of diabetic nephropathy, the therapeutic effects of angiogenesis inhibitors, including angiostatin, endostatin and tumstatin peptides, the isocoumarin NM-3, and vasohibin-1, have been reported.

Further analysis of the involvement of angiogenesis-related factors in the development of CKD is required. Determining the disease stage at which therapy is most effective and developing an effective drug delivery system targeting the kidney will be essential for pro-or anti-angiogenic strategies for patients with CKD.

VEGF blockade inhibits lymphocyte recruitment and ameliorates immune-mediated vascular remodeling

RATIONALE

There are conflicting data on the effects of vascular endothelial growth factor (VEGF) in vascular remodeling. Furthermore, there are species-specific differences in leukocyte and vascular cell biology and little is known about the role of VEGF in remodeling of human arteries.

OBJECTIVE

We sought to address the role of VEGF blockade on remodeling of human arteries in vivo.

METHODS AND RESULTS

We used an anti-VEGF antibody, bevacizumab, to study the effect of VEGF blockade on remodeling of human coronary artery transplants in severe combined immunodeficient mice. Bevacizumab ameliorated peripheral blood mononuclear cell-induced but not interferon-gamma-induced neointimal formation. This inhibitory effect was associated with a reduction in graft T-cell accumulation without affecting T-cell activation. VEGF enhanced T-cell capture by activated endothelium under flow conditions. The VEGF effect could be recapitulated when a combination of recombinant intercellular adhesion molecule 1 and vascular cell adhesion molecule-1 rather than endothelial cells was used to capture T cells. A subpopulation of CD3+ T cells expressed VEGF receptor (VEGFR)-1 by immunostaining and FACS analysis. VEGFR-1 mRNA was also detectable in purified CD4+ T cells and Jurkat and HSB-2 T-cell lines. Stimulation of HSB-2 and T cells with VEGF triggered downstream ERK phosphorylation, demonstrating the functionality of VEGFR-1 in human T cells.

CONCLUSIONS

VEGF contributes to vascular remodeling in human arteries through a direct effect on human T cells that enhances their recruitment to the vessel. These findings raise the possibility of novel therapeutic approaches to vascular remodeling based on inhibition of VEGF signaling.

Effect of fluoride on calcium ion concentration and expression of nuclear transcription factor kappa-B ρ65 in rat hippocampus

The study investigated the neurotoxicity of drinking water fluorosis in rat hippocampus. Just weaning male Sprague-Dawley (SD) rats were given 15, 30, 60 mg/L NaF solution and tap water for 9 months. The calcium ion concentration ([Ca(2+)]) in synaptosomes was measured by double wavelength fluorescence spectrophotometer and the expression level of nuclear transcription factor kappa-B ρ65 (NF-κB ρ65) in hippocampal CA3 region was measured by immunohistochemistry. The results showed that [Ca(2+)] significantly increased (F = 33.218, P < 0.01) in moderate fluoride group compared with the control group, and the expression level of NF-κB ρ65 in CA3 region presented an increasing trend as fluoride concentration increased. These results indicate that increase of synaptosomes [Ca(2+)] and NF-κB ρ65 expression level may be the molecular basis of central nervous system damage caused by chronic fluoride intoxication. NF-κB ρ65 in CA3 region is probably a target molecule for fluorosis.

Role of the VEGF 936 C/T polymorphism in diabetic microvascular complications in type 2 diabetic patients

AIM

Vascular endothelial growth factor (VEGF) is important in the pathogenesis of diabetic microvascular complications and the genetic polymorphism of this gene may contribute to the development and progression of diabetic microvascular complications. In this study, we investigated whether a genetic polymorphism of VEGF is associated with diabetic complications.

METHODS

A total of 398 type 2 diabetic patients and 526 healthy controls were enrolled. The study subjects were divided based on the state of nephropathy, retinopathy and neuropathy. The VEGF 936 C/T polymorphism was evaluated using standard PCR techniques, and plasma and urinary levels of VEGF were determined by enzyme-linked immunosorbent assay.

RESULTS

There was no difference in VEGF genotype distribution between the control and diabetic patients based on the state of diabetic nephropathy and neuropathy. However, a higher frequency of the TT genotype was observed in patients with proliferative diabetic retinopathy. Additionally, plasma levels of VEGF were significantly higher in the TT genotype. However, urinary levels of VEGF did not show a significant relationship with the VEGF genotype. Urinary VEGF levels showed a significant relationship with urinary albumin excretion, proteinuria, serum creatinine level and creatinine clearance, as well as fasting blood glucose levels, postprandial 2 h glucose levels and C-reactive protein.

CONCLUSION

Our study suggests that the 936 C/T polymorphism of the VEGF gene may be an important factor determining plasma VEGF levels and that its polymorphism is related with diabetic retinopathy. Urinary levels of VEGF are not associated with plasma VEGF levels and associated with the stage of diabetic nephropathy.

Immunological mechanisms in the pathogenesis of diabetic retinopathy

There is an accumulating body of evidence that immunological mechanisms play a prominent role in the pathogenesis of diabetic retinopathy (DR), which is characterized by many features typical of inflammation. The upregulation of cytokines and other inflammatory mediators leading to persistent low-grade inflammation and an influx of leukocytes, is believed to contribute actively to DR-associated damage to the retinal vasculature and retinal neovascularization. This review will describe preclinical and clinical studies that document an inflammatory basis for DR and that support the use of nonsteroidal anti-inflammatory drugs, corticosteroids, and anti-vascular endothelial growth factor agents in its treatment. In addition, emerging therapeutic approaches based on ongoing investigations will be discussed, including those involving blockade of angiotensin receptors and other molecular targets such as tumor necrosis factor-alpha.

Association of vascular endothelial growth factor C-634 g polymorphism in taiwanese children with Kawasaki disease

High expression of circulating vascular endothelial growth factor (VEGF) has been reported in patients with Kawasaki disease (KD). In the pathophysiology of KD, VEGF is considered to be involved, especially in the development of coronary artery lesions. This study aimed to examine whether the VEGF-634 promoter polymorphism is a marker of KD susceptibility or severity in Chinese patients in Taiwan. The study included 93 KD patients and 96 normal control subjects. Genotype and allelic frequencies for the VEGF gene polymorphism in the two groups were compared. The number of individuals with the VEGF-634 G/G genotype was significantly greater among the patients with KD than among the healthy control subjects (p = 0.011). The odds ratio for the development of KD in individuals with the VEGF-634 G/G genotype was found to be 2.03 (95% confidence interval [CI], 1.14-3.63) compared with the VEGF-634 G/C and VEGF-634 C/C genotypes. No significant difference was observed in the genotype or allelic frequencies of VEGF C-634 G polymorphism between the patients with and those without coronary artery lesions. In conclusion, the results suggest that VEGF-634 G/G genotype may be involved in the development of KD in Taiwanese children.

Oxidant stress impairs in vivo reendothelialization capacity of endothelial progenitor cells from patients with type 2 diabetes mellitus: restoration by the peroxisome proliferator-activated receptor-gamma agonist rosiglitazone

BACKGROUND

Endothelial progenitor cells (EPCs) are thought to contribute to endothelial recovery after arterial injury. We therefore compared in vivo reendothelialization capacity of EPCs derived from patients with diabetes mellitus and healthy subjects. Moreover, we examined the effect of treatment with the peroxisome proliferator-activated receptor-gamma agonist rosiglitazone on oxidant stress, nitric oxide (NO) bioavailability, and the in vivo reendothelialization capacity of EPCs from diabetic individuals.

METHODS AND RESULTS

In vivo reendothelialization capacity of EPCs from diabetic patients (n=30) and healthy subjects (n=10) was examined in a nude mouse carotid injury model. Superoxide and NO production of EPCs was determined by electron spin resonance spectroscopy. Thirty patients with diabetes mellitus were randomized to 2 weeks of rosiglitazone (4 mg BID p.o.) or placebo treatment. In vivo reendothelialization capacity of EPCs derived from diabetic subjects was severely reduced compared with EPCs from healthy subjects (reendothelialized area: 8+/-3% versus 37+/-10%; P<0.001). EPCs from diabetic individuals had a substantially increased superoxide production and impaired NO bioavailability. Small-interfering RNA silencing of NAD(P)H oxidase subunit p47(phox) reduced superoxide production and restored NO bioavailability and in vivo reendothelialization capacity of EPCs from diabetic patients. Importantly, rosiglitazone therapy normalized NAD(P)H oxidase activity, restored NO bioavailability, and improved in vivo reendothelialization capacity of EPCs from diabetic patients (reendothelialized area: placebo versus rosiglitazone, 8+/-1% versus 38+/-5%; P<0.001).

CONCLUSIONS

In vivo reendothelialization capacity of EPCs derived from individuals with diabetes mellitus is severely impaired at least partially as a result of increased NAD(P)H oxidase-dependent superoxide production and subsequently reduced NO bioavailability. Rosiglitazone therapy reduces NAD(P)H oxidase activity and improves reendothelialization capacity of EPCs from diabetic individuals, representing a potential novel mechanism whereby peroxisome proliferator-activated receptor-gamma agonism promotes vascular repair.

Decreased Expression of VEGF-A in Rat Experimental Autoimmune Encephalomyelitis and in Cerebrospinal Fluid Mononuclear Cells from Patients with Multiple Sclerosis

Vascular endothelial growth factor A (VEGF-A) stimulates angiogenesis, but is also pro-inflammatory and plays an important role in the development of neurological disease, where it can have both attenuating and exacerbating effects. VEGF-B, a related molecule, is highly expressed in the central nervous system and seems to be important in neurological injury. A few studies have indicated that VEGF-A may play a role in the pathogenesis of multiple sclerosis (MS), but the role of VEGF-B has not been studied. We have studied the expression of VEGF-A, -B and their receptors by mRNA in situ hybridization, immunohistochemistry and real-time PCR in spinal cord from LEW rats with experimental autoimmune encephalomyelitis (EAE) and in cerebrospinal fluid (CSF) and blood samples from MS patients. Whereas VEGF-A is downregulated in glia in EAE, the infiltrating inflammatory cells are positive for VEGF-A. Expression of VEGF-B and the VEGF receptors is unaltered. In addition, the levels of VEGF-A mRNA in mononuclear cells [corrected] in CSF are lower in MS patients compared with controls. These results demonstrate a complex regulation of VEGF-A during neuroinflammation and suggest that VEGF-B is not involved in the pathogenesis of MS.

Analysis of glomerular VEGF mRNA and protein expression in murine mesangioproliferative glomerulonephritis

Capillary repair is crucial in the healing of glomerulonephritis (GN). The vascular endothelial growth factor (VEGF) has pro-angiogenic properties and plays an important role in glomerular capillary regeneration. Habu Snake Venom (HSV) GN, a murine model for mesangioproliferative GN, was induced in uninephrectomized C57/BL6 mice. Glomerular damage and capillary repair were assessed using morphometry, stereology, and confocal laser scanning microscopy. Mesangiolytic glomeruli were microdissected (days 1,3,7,14) using laser capture microdissection technique. VEGF mRNA expression was analyzed by real-time polymerase chain reaction and compared to intact glomeruli of healthy controls. Spatiotemporal VEGF gene and protein expression was determined using nonradioactive in situ hybridization and immunohistochemistry. On day 1, diseased animals developed focal mesangiolysis paralleled by a significant decrease in length density of glomerular capillaries that gradually returned to baseline levels thereafter, indicating capillary growth in response to initial injury. Glomerular VEGF mRNA expression increased on day 3 and returned back to baseline and beyond at day 14 when the glomerular recovery process was completed. Similarly, glomerular VEGF protein expression tended to be higher on day 3. The present study documents temporarily increased glomerular VEGF gene and protein expression during the healing of HSV GN, suggesting a potential role of VEGF in the repair of mesangiolytic glomerular damage.

IL-1beta induces VEGF, independently of PGE2 induction, mainly through the PI3-K/mTOR pathway in renal mesangial cells

Vascular endothelial growth factor (VEGF) could play a relevant role in angiogenesis associated with chronic allograft nephropathy. Interleukin-1beta (IL-1beta) has a key role in inflammatory response. It induces prostaglandin (PG) E2, which is involved in VEGF release by some normal and tumor cells. In the present work, we studied the effect of IL-1beta on VEGF release by rat mesangial cells, the transduction signal, and whether or not PGE2 is involved in this effect. IL-1beta induced a time-dependent formation of VEGF (analyzed by enzyme-linked immunosorbent assay) and PGE2 (analyzed by enzyme immunoassay). The latter correlated with microsomal-PGE-synthase (mPGES)-1 expression rather than with cyclooxygenase (COX)-2 in terms of protein, determined by Western blotting. No effect of IL-1beta on COX-1, cytosolic PGES, or mPGES-2 expression was observed. Indomethacin exerted a nonsignificant effect on IL-1beta-induced VEGF, and exogenously added PGE2 exhibited a nonsignificant stimulatory effect on VEGF formation. SB 203580, a p38 mitogen-activated protein kinase inhibitor, weakly inhibited the induction of VEGF by IL-1beta in a concentration-dependent manner, whereas LY 294002, a phosphoinoside 3-kinase (PI3-K) inhibitor, and rapamycin, a mammalian target of rapamycin (mTOR) inhibitor, strongly inhibited both IL-1beta- and tumor necrosis factor-alpha-induced VEGF formation in a concentration-dependent manner. Rapamycin also decreased glomerular VEGF levels in the anti-Thy1.1 model of experimental glomerulonephritis. In conclusion, the PI3-K-mTOR pathway seems to be essential in cytokine-induced release of VEGF in mesangial cells.

Increased serum level of vascular endothelial growth factor in Mycobacterium avium complex infection

OBJECTIVE

Pulmonary infection caused by Mycobacterium avium complex (MAC) is one of the granulomatous diseases which are associated with the expression of vascular endothelial growth factor (VEGF). The aim of the present study was to clarify the association of VEGF with the pathogenesis of MAC infection.

METHODOLOGY

The serum VEGF levels in 46 patients with pulmonary MAC infection were compared with those in 16 normal control subjects. Pulmonary lesions were evaluated using chest CT. In 20 patients, after treatment, serum VEGF levels were measured and chest CT performed again to evaluate pulmonary response to treatment.

RESULTS

Infected patients had higher serum VEGF levels than controls (435.2 +/- 29.1 vs. 167.0 +/- 10.6 pg/mL, P < 0.0001), and serum VEGF level correlated with the extent of disease. The serum VEGF levels in 14 patients who underwent treatment and exhibited an improvement in their pulmonary lesions decreased significantly compared with the results pretreatment (509.0 +/- 60.7 vs. 303.6 +/- 65.3 pg/mL, P = 0.0092). In infected patients, alveolar macrophages, epithelioid cells and multinucleated giant cells exhibited VEGF overexpression on immunohistochemical staining.

CONCLUSIONS

This study suggests that VEGF may be associated with the pathogenesis of pulmonary MAC infection. Additionally, serum VEGF levels may be a useful surrogate marker for evaluating the extent of disease and of the response to treatment.

Local VEGF activity but not VEGF expression is tightly regulated during diabetic nephropathy in man

Several studies have implicated the angiogenic cytokine vascular endothelial growth factor (VEGF) in the development of diabetic nephropathy, but no data are available about its local activity during human disease. Glomeruli from 52 archival biopsies from type II diabetics were evaluated and compared to 10 renal biopsies without kidney disease (controls). Glomerulosclerosis, capillary rarefaction, glomerular and endothelial cell proliferation, apoptosis, VEGF expression, as well as receptor-bound VEGF indicating local VEGF activity, and phosphorylation of the signal transduction molecule Akt were investigated. Owing to substantial heterogeneity of glomerular lesions in individual biopsies, these parameters were correlated with the degree of injury in individual glomeruli rather than biopsies. Severe glomerular capillary rarefaction was linked to the degree of glomerulosclerosis. While cellular apoptosis was detected independent of the stage of injury, endothelial cell proliferation indicating capillary repair was markedly increased only in mildly/moderately injured glomeruli. In controls, VEGF was predominantly expressed in podocytes, whereas receptor-bound VEGF was confined to the glomerular endothelium. VEGF expression was increased in all diabetic glomeruli by many different cell types. In contrast, VEGF receptor activation was increased predominantly in the endothelium of only mildly injured glomeruli, but significantly decreased in more severely injured glomeruli. Diabetic nephropathy is associated with glomerular capillary rarefaction. Despite overall increased glomerular VEGF, the decreased receptor-bound VEGF on the endothelium may be an indicator of an insufficient capillary repair reaction.

Functional polymorphisms in the vascular endothelial growth factor gene are associated with development of end-stage renal disease in males

This study elucidates the genetic role of vascular endothelial growth factor (VEGF) as a predisposing factor for progression of chronic kidney disease. Single-nucleotide polymorphisms were genotyped and haplotype structures were determined in the 3' untranslated region (UTR) of VEGF gene, and the distribution of each haplotype in male patients with ESRD (n=101) and healthy male control subjects (n=189) was examined. The 936C/T and 1451C/T polymorphisms in the 3' UTR were in nearly absolute linkage disequilibrium, and haplotype analysis demonstrated that they were the primary responsible single-nucleotide polymorphisms. The distribution of the 936CC-1451CC genotype was significantly more frequent among patients with ESRD than among the age-matched healthy control subjects. In addition to case-control association study, the 936CC-1451CC genotype was also associated with significantly higher plasma VEGF levels in healthy individuals, but a significant association was found only in males, not in females. We also examined the effect of the 936C-1451C haplotype on mRNA stability. Consistent with the results of plasma VEGF levels, mRNA carrying 936C-1451C haplotype showed higher stability. The 936CC-1451CC genotype in the 3' UTR showed not only susceptibility for ESRD but also higher plasma VEGF levels and mRNA stability, indicating the contribution of VEGF to chronic kidney disease progression, especially in males.

The role of vascular endothelial growth factor in ocular health and disease

The leading causes of blindness are retinal and choroidal diseases manifesting abnormal vessel permeability and growth. Scientists have sought to understand the mechanisms underlying these pathologic conditions with the hope of developing directed and effective pharmacologic therapies. Research has yielded important new mechanistic data, making possible the development of new drugs. One of the most important targets to have emerged is a secreted protein named vascular endothelial growth factor. This review will summarize the current state of our knowledge regarding this growth factor and outline some important questions that remain to be answered.

The role of vascular endothelial growth factor (VEGF) in renal pathophysiology

Vascular endothelial growth factor (VEGF) is an endothelial-specific growth factor that promotes endothelial cell proliferation, differentiation and survival, mediates endothelium-dependent vasodilatation, induces microvascular hyperpermeability and participates in interstitial matrix remodeling. In the kidney, VEGF expression is most prominent in glomerular podocytes and in tubular epithelial cells, while VEGF receptors are mainly found on preglomerular, glomerular, and peritubular endothelial cells. The role of VEGF in normal renal physiology is essentially unknown. The absence of prominent effects of VEGF blockade in normal experimental animals suggests a limited function during homeostasis, although a role in the formation and maintenance of glomerular capillary endothelial fenestrations has been suggested. VEGF and its receptors are up-regulated in experimental animals and humans with type 1 and type 2 diabetes. Inhibition of VEGF has beneficial effects on diabetes-induced functional and structural alterations, suggesting a deleterious role for VEGF in the pathophysiology of diabetic nephropathy. VEGF is required for glomerular and tubular hypertrophy and proliferation in response to nephron reduction, and loss of VEGF is associated with the development of glomerulosclerosis and tubulointerstitial fibrosis in the remnant kidney. No firm conclusions on the role of VEGF in minimal change or membranous glomerulonephritis can be drawn. VEGF may be an essential mediator of glomerular recovery in proliferative glomerulonephritis. Glomerular and tubulointerstitial repair in thrombotic microangiopathy and cyclosporin nephrotoxicity may also be VEGF-dependent. In conclusion, VEGF is required for growth and proliferation of glomerular and peritubular endothelial cells. While deleterious in some, it may contribute to recovery in other forms of renal diseases.

From hyperglycemia to diabetic kidney disease: the role of metabolic, hemodynamic, intracellular factors and growth factors/cytokines

At present, diabetic kidney disease affects about 15-25% of type 1 and 30-40% of type 2 diabetic patients. Several decades of extensive research has elucidated various pathways to be implicated in the development of diabetic kidney disease. This review focuses on the metabolic factors beyond blood glucose that are involved in the pathogenesis of diabetic kidney disease, i.e., advanced glycation end-products and the aldose reductase system. Furthermore, the contribution of hemodynamic factors, the renin-angiotensin system, the endothelin system, and the nitric oxide system, as well as the prominent role of the intracellular signaling molecule protein kinase C are discussed. Finally, the respective roles of TGF-beta, GH and IGFs, vascular endothelial growth factor, and platelet-derived growth factor are covered. The complex interplay between these different pathways will be highlighted. A brief introduction to each system and description of its expression in the normal kidney is followed by in vitro, experimental, and clinical evidence addressing the role of the system in diabetic kidney disease. Finally, well-known and potential therapeutic strategies targeting each system are discussed, ending with an overall conclusion.

Transforming growth factor-beta1 stimulates vascular endothelial growth factor 164 via mitogen-activated protein kinase kinase 3-p38alpha and p38delta mitogen-activated protein kinase-dependent pathway in murine mesangial cells

Transforming growth factor-beta1 (TGF-beta1) is a potent inducer of extracellular matrix synthesis leading to progressive glomerular fibrosis. The intracellular signaling mechanisms involved in this process remain incompletely understood. The p38 mitogen-activated protein kinase (MAPK) is a major stress signal transducing pathway that is rapidly activated by TGF-beta1 in mesangial cells. We have previously demonstrated MKK3 as the immediate upstream MAPK kinase required for selective activation of p38 MAPK isoforms, p38alpha and p38delta, and stimulation of pro-alpha1(I) collagen by TGF-beta1 in murine mesangial cells. In this study, we further sought to determine MAPK kinase 3 (MKK3)-dependent TGF-beta1 responses by gene expression profiling analysis utilizing mesangial cells isolated from Mkk3-/- mice compared with Mkk3+/+ controls. Interestingly, vascular endothelial growth factor (VEGF) was identified as a TGF-beta1-induced gene affected by deletion of Mkk3. VEGF is a well known endothelial mitogen, whose actions in nonendothelial cell types are still not well understood. We confirmed that TGF-beta1 increased VEGF mRNA and protein synthesis of VEGF164 and VEGF188 isoforms in wild-type mesangial cells. However, in the Mkk3-/- mesangial cells, both TGF-beta1-induced VEGF mRNA and VEGF164 protein expression were inhibited, whereas TGF-beta1-induced VEGF188 protein expression was unaffected. Furthermore, transfection of dominant negative mutants of p38alpha and p38delta resulted in marked inhibition of TGF-beta1-induced VEGF164 expression but not VEGF188, and treatment with recombinant mouse VEGF164 increased collagen and fibronectin mRNA expression in mesangial cells. Taken together, our findings suggest a critical role for the MKK3-p38alpha and p38delta MAPK pathway in mediating VEGF164 isoform-specific stimulation by TGF-beta1 in mesangial cells. Further, VEGF164 stimulates collagen and fibronectin expression in mesangial cells and thus in turn enhances TGF-beta1-induced extracellular matrix and may play an important role in progressive glomerular fibrosis.

Vascular factors altered in glucose-treated mesangial cells and diabetic glomeruli. Changes in vascular factors impair endothelial cell growth and matrix

We studied the effect of a high glucose (HG) environment on the vascular factors that are secreted by mesangial cells, and regulate endothelial growth and mesangial matrix deposition. To this effect, we measured the vascular factors in the glomeruli of streptozotocin-induced diabetic kidneys and in mesangial cells exposed to a HG concentration. We then transferred the media of mesangial cells previously exposed to high glucose to cultured endothelial cells to study the effects on endothelial growth, matrix formation, and in vitro capillary proliferation. In 1-week diabetic kidneys, glomerular vascular endothelial growth factor (VEGF) and angiopoietin-1 were inhibited by 38 and 57%, respectively, but angiopoietin-2 was increased by 318%. We found similar results in mesangial cells exposed to HG. There was a decrease of VEGF (50% by enzyme immunoassay, 27% by mRNA), decrease of angiopoietin-1 (65% by mRNA), and a much greater increase of angiopoietin-2 (280% by immunoassay, 523% by mRNA). Compared to controls, the media of mesangial cells previously exposed to HG impaired endothelial cell growth by 61%, increased extracellular matrix by 100%, and decreased capillary formation by 90%. We conclude that high ambient glucose alters the secretion of vascular factors elaborated by mesangial cells, resulting in an expansion of the endothelial cell matrix and disruption of capillary structure.

The Role of Vascular Endothelial Growth Factor in the Kidney in Health and Disease

Vascular endothelial growth factor (VEGF) is a potent endothelial cell mitogen, angiogenic factor and enhancer of vascular permeability. Expressed in the epithelial cells of the developing glomerulus and tubular epithelium, VEGF plays an important role in the development and maintenance of the early vasculature of the kidney. Here, we review the available literature regarding the expression and function of VEGF both in the developing and healthy adult kidney. Furthermore, we highlight how VEGF expression is altered in the diseased kidney and how this modulated expression may impact on and reflect underlying functional changes occurring during the disease process. As discussed, many controversial issues remain, particularly concerning the role of VEGF in the diseased kidney. That VEGF has been proposed as a potential future therapeutic target for the management of some renal diseases requires first that the precise role of VEGF in the normal kidney and various renal pathologies be further and more clearly defined.

Relevance of monocytic features for neovascularization capacity of circulating endothelial progenitor cells

BACKGROUND

Transplantation of ex vivo expanded circulating endothelial progenitor cells (EPCs) from peripheral blood mononuclear cells improves the neovascularization after critical ischemia. However, the origin of the endothelial progenitor lineage and its characteristics have not yet been clearly defined. Therefore, we investigated whether the phenotype and functional capacity of EPCs to improve neovascularization depend on their monocytic origin.

METHODS AND RESULTS

Monocytic CD14+ cells were isolated from mononuclear cells and incubated on fibronectin-coated dishes in endothelial medium in the presence of vascular endothelial growth factor. After 4 days of cultivation, adherent cells deriving from CD14+ or CD14- mononuclear cells showed equal expression of endothelial marker proteins and capacity for clonal expansion as determined by measuring endothelial colony-forming units. In addition, transplanted EPCs (5x10(5) cells) deriving from CD14+ or CD14- cells were incorporated into vascular structures of nude mice after hind-limb ischemia and significantly improved neovascularization from 0.27+/-0.12 (no cells) to 0.66+/-0.12 and 0.65+/-0.17, respectively (P<0.001; laser Doppler-derived relative blood flow). In contrast, no functional improvement of neovascularization was detected when freshly isolated CD14+ mononuclear cells without ex vivo expansion were used (0.33+/-0.17). Moreover, macrophages or dendritic cells differentiated from isolated CD14+ cells were significantly less effective in improving neovascularization than EPCs cultivated from the same starting population (P<0.01).

CONCLUSIONS

These data demonstrate that EPCs can be generated from nonmonocytic CD14- peripheral blood mononuclear cells and exhibit a unique functional activity to improve neovascularization after hind-limb ischemia.

Role of VEGF in kidney development, microvascular maintenance and pathophysiology of renal disease

Vascular endothelial growth factor, VEGF, is essential for endothelial cell differentiation (vasculogenesis) and for the sprouting of new capillaries from preexisting vessels (angiogenesis). In addition, there is strong evidence that VEGF is a survival factor allowing the cells to survive and proliferate under conditions of extreme stress. Hypoxia is a key regulator of VEGF gene expression. Besides hypoxia, many cytokines, hormones and growth factors can up-regulate VEGF mRNA expression in various cell types. VEGF is present in the glomerulus of both the fetal and adult kidney. The VEGF produced by glomerular epithelial cell may be responsible for maintenance of the fenestrated phenotype of glomerular epithelial cells, thus facilitating the high rate of glomerular ultrafiltration. But there is little known about the role of VEGF in the tubule. VEGF is thought to be involved in many kinds of kidney diseases. Whereas VEGF has a beneficial role in the pathogenesis in some diseases, it does harmful action in others. Because VEGF is known to be associated with the pathogenesis of some diseases, such as diabetic nephropathy, renal tumor and polycystic kidney disease, the study about the role of VEGF is going to be a target for disease control. On the other hand, an attempt at enhancing the role of VEGF has to be made at diseases like several ARF models and experimental glomerulonephritis.

IGF-I induces vascular endothelial growth factor in human mesangial cells via a Src-dependent mechanism

BACKGROUND

Both insulin-like growth factor-I (IGF-I) and vascular endothelial growth factor (VEGF) have been implicated in the pathogenesis of early renal dysfunction in diabetes. We investigated whether IGF-I affects VEGF gene expression and protein secretion in human mesangial cells. Furthermore, we studied the intracellular signaling pathway involved and the interaction of IGF-I with mechanical stretch, a known VEGF inducer.

METHODS

Human mesangial cells were exposed to IGF-I in the presence and in the absence of (1) anti-IGF-I type I receptor antibody (alpha IR3) (1 microg/mL), a monoclonal antibody blocking the IGF-I type I receptor; (2) wortmannin (600 nmol/L), a phosphatidylinositol 3-kinase (PI3K) inhibitor; (3) 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP2), a specific Src inhibitor (10 micromol/L); and (4) cyclic stretch (approximately 10% elongation).

RESULTS

IGF-I induced a dose-dependent increase in VEGF protein levels (10(-11) mol/L, 5%; 10(-10) mol/L, 14%; 10(-9) mol/L, 46%; 10(-8) mol/L, 66%; 10(-7) mol/L, 68%; P < 0.001). IGF-I-induced VEGF production rose by 6 hours with a peak at 12 hours, and declined by 24 hours (52%, 72%, and 34%, respectively; P < 0.01 at 12 hours). A corresponding 50% increase in VEGF mRNA levels was seen at 6 hours (P < 0.01). IGF-I-induced VEGF protein secretion was not affected by the addition of wortmannin (IGF-I, 76% vs. IGF-I + wortmannin, 79% increase over control; P = NS), but was abolished by alpha IR3 (IGF-I, 69% vs. IGF-I +alpha IR3, 0%; P < 0.001) and significantly reduced by PP2 (IGF-I, 50% vs. IGF-I + PP2, 14%; P < 0.01). Simultaneous exposure of human mesangial cells to both IGF-I and stretch failed to further increase VEGF production (IGF-I, 1.49 +/- 0.05; stretch, 1.76 +/- 0.05; and IGF-I + stretch, 1.83 +/- 0.11).

CONCLUSION

IGF-I induces VEGF gene expression and protein secretion in human mesangial cells via a Src-dependent mechanism.

Polymorphisms of the vascular endothelial growth factor and susceptibility to diabetic microvascular complications in patients with type 1 diabetes mellitus

There is increasing evidence implicating genetic factors in the susceptibility to diabetic microvascular complications. Recent studies suggest that increased expression of the cytokine vascular endothelial growth factor (VEGF) may play a role in the pathogenesis of diabetic complications. A number of polymorphisms in the promoter region of the VEGF gene have been identified. The aim was to investigate whether an 18 base pair (bp) deletion (D)/insertion (I) polymorphism at position -2549 in the promoter region of the VEGF gene is associated with the susceptibility to diabetic microvascular complications. Two hundred and thirty-two patients with type 1 diabetes mellitus (T1DM) and 141 normal healthy controls were studied. The D/D genotype was significantly increased in those patients with nephropathy (n=102) compared to those with no complications after 20 years duration of diabetes (uncomplicated, n=66) (40.2% vs. 22.7%, respectively, chi(2)=5.5, P<.05). The combination of polymorphisms of VEGF together with the aldose reductase (ALR2) gene showed that in the nephropaths, 8 of the 83 subjects had the VEGF I allele together with the Z+2 5'ALR2 allele compared with 27 of the 62 uncomplicated patients (chi(2)=26.7, P<.00001). The functional role of the D/I polymorphism was examined by cloning the region into a luciferase reporter assay system and transient transfection into HepG2 cells. The construct containing the 18 bp deletion had a 1.95-fold increase in transcriptional activity compared with its counterpart that had the insert (P<.01). These results suggest that polymorphisms in the promoter region of the VEGF gene together with the ALR2 may be associated with the pathogenesis of diabetic nephropathy.

Renal ischemia-reperfusion increases endothelial VEGFR-2 without increasing VEGF or VEGFR-1 expression

BACKGROUND

Hypoxia is a potent stimulus to angiogenesis. Expression of the angiogenic growth factor vascular endothelial growth factor (VEGF) and its receptors (VEGFR-1 and VEGFR-2) is up-regulated by hypoxia in a variety of organs and cell lines. We have previously reported that VEGF expression is not increased in renal ischemia-reperfusion injury, although tubular cells concentrate VEGF at their basolateral surface. In this study we assess whether altered VEGF receptor expression compensates for the lack of VEGF regulation during renal ischemia-reperfusion injury.

METHODS

VEGFR-1 mRNA expression was assessed by Northern blotting and semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). VEGFR-2 mRNA expression was analyzed by Northern blotting and in situ hybridization (ISH), while VEGFR-2 protein expression was studied using immunohistochemistry. VEGF mRNA expression was assessed by ISH.

RESULTS

VEGFR-2 mRNA and protein expression were up-regulated without an increase in VEGF or VEGFR-1 expression. Normal kidneys showed low-level VEGFR-2 mRNA and protein expression in glomerular and peritubular endothelium. Following ischemia and ischemia-reperfusion, a marked increase in VEGFR-2 mRNA and protein expression was seen (2- to 4-fold). Most prominent was VEGFR-2 mRNA up-regulation in the glomerulus although, surprisingly, increased protein was not demonstrated here. ISH showed that VEGF mRNA was not up-regulated in this model, confirming our previous findings for VEGF.

CONCLUSION

VEGF and VEGFR-1 expression are not increased by renal ischemia and ischemia-reperfusion injury. Instead, endothelial expression of VEGFR-2 is increased. VEGFR-2 up-regulation in renal ischemia-reperfusion may be important in mediating the mitogenic and anti-apoptotic actions of VEGF on endothelial cells, thereby preserving the integrity of the endothelium and the potential for blood supply to ischemic tissues.

Retinal vascular endothelial growth factor induces intercellular adhesion molecule-1 and endothelial nitric oxide synthase expression and initiates early diabetic retinal leukocyte adhesion in vivo

Leukocyte adhesion to the diabetic retinal vasculature results in early blood-retinal barrier breakdown, capillary nonperfusion, and endothelial cell injury and death. Previous work has shown that intercellular adhesion molecule-1 (ICAM-1) and CD18 are required for these processes. However the relevant in vivo stimuli for ICAM-1 and CD18 expression in diabetes remain unknown. The current study investigated the causal role of endogenous vascular endothelial growth factor (VEGF) and nitric oxide in initiating these events. Diabetes was induced in Long-Evans rats with streptozotocin, resulting in a two- to threefold increase in retinal leukocyte adhesion. Confirmed diabetic animals were treated with a highly specific VEGF-neutralizing Flt-Fc construct (VEGF TrapA(40)). Retinal ICAM-1 mRNA levels in VEGF TrapA(40)-treated diabetic animals were reduced by 83.5% compared to diabetic controls (n = 5, P < 0.0001). VEGF TrapA(40) also potently suppressed diabetic leukocyte adhesion in retinal arterioles (47%, n = 11, P < 0.0001), venules (36%, n = 11, P < 0.0005), and capillaries (36%, n = 11, P < 0.001). The expression of endothelial nitric oxide synthase (eNOS), a downstream mediator of VEGF activity, was increased in diabetic retina, and was potently suppressed with VEGF TrapA(40) treatment (n = 8, P < 0.005). Further, VEGF TrapA(40) reduced the diabetes-related nitric oxide increases in the retinae of diabetic animals. The inhibition of eNOS with N-omega-nitro-L-arginine methyl ester also potently reduced retinal leukocyte adhesion. Although neutrophil CD11a, CD11b, and CD18 levels were increased in 1-week diabetic animals, VEGF TrapA(40) did not alter the expression of these integrin adhesion molecules. Taken together, these data demonstrate that VEGF induces retinal ICAM-1 and eNOS expression and initiates early diabetic retinal leukocyte adhesion in vivo. The inhibition of VEGF bioactivity may prove useful in the treatment of the early diabetic retinopathy.

Vascular endothelial growth factor enhances glomerular capillary repair and accelerates resolution of experimentally induced glomerulonephritis

Vascular endothelial growth factor (VEGF) regulates angiogenesis through endothelial cell proliferation and plays an important role in capillary repair in damaged glomeruli. We tested the hypothesis that VEGF might be beneficial in rats with severe glomerular injury in glomerulonephritis (GN) based on its angiogenic and vascular remodeling properties. Acute GN with severe glomerular destruction was induced in rats by injection of anti-Thy-1.1 antibody (day 0) and Habu-snake venom (day 1). Rats were intraperitoneally injected with recombinant human VEGF(165) (10 microg/100 g body wt/day) or vehicle from day 2 to day 9, and monitored changes in glomerular capillaries, development of glomerular inflammation, and progression to glomerular sclerosis after acute glomerular destruction in both groups. Rats that received anti-Thy-1.1 antibody and Habu-snake venom showed severe mesangiolysis and marked destruction of capillary network on day 2. VEGF was expressed on glomerular epithelial cells, proliferating mesangial cells, and some infiltrating leukocytes, and VEGF(165) protein levels increased in damaged glomeruli during day 5 to day 7. Normal, damaged, and regenerating glomerular endothelial cells expressed VEGF receptor flk-1. However, endothelial cell proliferation and capillary repair was rare in vehicle-treated rats with severe glomerular damage, which progressed to global sclerosis and chronic renal failure by week 8. In contrast, in the VEGF-treated group, VEGF(165) significantly enhanced endothelial cell proliferation and capillary repair in glomeruli by day 9 (proliferating endothelial cells: VEGF(165), 4.3 +/- 1.1; control, 2.2 +/- 0.9 cells on day 7, P < 0.001; and glomerular capillaries: VEGF(165), 24.6 +/- 4.8; control, 16.9 +/- 3.4 capillaries on day 7, P < 0.01). Thereafter, damaged glomeruli gradually recovered after development of capillary network by week 8, and significant improvement of renal function was evident in the VEGF-treated group during week 8 (creatinine: VEGF(165), 0.3 +/- 0.1; control, 2.6 +/- 0.9 mg/dl, P < 0.001; proteinuria: VEGF(165), 54 +/- 15; control, 318 +/- 60 mg/day, P < 0.001). We conclude that the beneficial effect of VEGF(165) in severe glomerular injury in GN emphasizes the importance of capillary repair in the resolution of GN, and may allow the design of new therapeutic strategies against severe GN.