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AUF1-RGG peptides up-regulate the VEGF antagonist, soluble VEGF receptor-1 (sFlt-1).

ABSTRACT: The macrophage is essential to the innate immune response, but also contributes to human disease by aggravating inflammation. Under severe inflammation, macrophages and other immune cells over-produce immune mediators, including vascular endothelial growth factor (VEGF). The VEGF protein stimulates macrophage activation and induces macrophage migration. A natural inhibitor of VEGF, the soluble VEGF receptor (sFlt-1) is also produced by macrophages and sFlt-1 has been used clinically to block VEGF. In macrophages, we have shown that the mRNA regulatory protein AUF1/hnRNP D represses VEGF gene expression by inhibiting translation of AURE-regulated VEGF mRNA. Peptides (AUF1-RGG peptides) that are modeled on the arginine-glycine-glycine (RGG) motif in AUF1 also block VEGF expression. This report shows that the AUF1-RGG peptides reduce two other AURE-regulated genes, TNF and GLUT1. Three alternative splice variants of sFlt-1 contain AURE in their 3'UTR, and in an apparent paradox, AUF1-RGG peptides stimulate expression of these three sFlt-1 Variants. The AUF1-RGG peptides likely act by distinct mechanisms with complimentary effects to repress VEGF gene expression and over-express the endogenous VEGF blocking agent, sFlt-1. The AUF1-RGG peptides are novel reagents that reduce VEGF and other inflammatory mediators, and may be useful tools to suppress severe inflammation.

SUBMITTER: Fellows A

PROVIDER: S-EPMC3770750 | biostudies-literature | 2013 Oct

REPOSITORIES: biostudies-literature

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AUF1-RGG peptides up-regulate the VEGF antagonist, soluble VEGF receptor-1 (sFlt-1).

Fellows Abigail A Mierke Dale F DF Nichols Ralph C RC

Cytokine 20130614 1

The macrophage is essential to the innate immune response, but also contributes to human disease by aggravating inflammation. Under severe inflammation, macrophages and other immune cells over-produce immune mediators, including vascular endothelial growth factor (VEGF). The VEGF protein stimulates macrophage activation and induces macrophage migration. A natural inhibitor of VEGF, the soluble VEGF receptor (sFlt-1) is also produced by macrophages and sFlt-1 has been used clinically to block VEG ...[more]

PMID: 23769804

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Project description:BackgroundEndothelial injury, which may present clinically as hypertension, proteinuria and increased von Willebrand Factor (vWF) level, is a common manifestation in IgA nephropathy (IgAN). However, causal factors for endothelial injury in IgAN are not completely understood. An imbalance of vascular endothelial growth factor/Soluble fms-like tyrosine kinase-1 (VEGF/sFlt-1) has been observed in many diseases with endothelial dysfunction, including pre-eclampsia and diabetic retinopathy, but whether it contributes to endothelial injury in IgAN requires further exploration.MethodsInitially, 96 IgAN patients and 22 healthy volunteers were enrolled as a discovery cohort. VEGF/sFlt-1, sFlt-1 and VEGF levels were compared between patients with IgAN and healthy volunteers to explore the underlying factors that contribute to endothelial injury in IgAN. The identified contributor (sFlt-1) was further confirmed in a replication cohort, which included 109 IgAN patients and 30 healthy volunteers. Correlations of sFlt-1 with hypertension, proteinuria, Oxford-E score and plasma vWF were further evaluated in the combined 205 patients with IgAN.ResultsVEGF/sFlt-1 levels were significantly lower in IgAN patients than healthy volunteers (0.33±0.27 vs. 0.43±0.22, p = 0.02) in the discovery cohort. Within the ratio, plasma sFlt-1 levels were significantly elevated (101.18±25.19 vs. 79.73±18.85 pg/ml, p<0.001), but plasma VEGF levels showed no significant differences. Elevated sFlt-1 levels in the replication cohort were confirmed in IgAN patients (93.40±39.78 vs. 71.92±15.78 pg/ml, p<0.001). Plasma sFlt-1 levels in IgAN patients correlated with proteinuria (severe (>3.5 g/d) vs. moderate (1-3.5 g/d) vs. mild (<1 g/d) proteinuria: 115.95±39.09 vs. 99.89±28.55 vs. 83.24±33.92 pg/ml; severe vs. mild: p<0.001, moderate vs. mild p = 0.001, severe vs. moderate: p = 0.014), hypertension (with vs. without hypertension: 107.87±31.94 vs. 87.32±32.76 pg/ml, p = 0.015) and vWF levels (r = 0.161, p = 0.021).ConclusionsThe present study found elevated sFlt-1 in IgAN patients and further identified its correlation with proteinuria, hypertension and vWF levels. These results suggested that elevated sFlt-1 contributes to endothelial injury in IgAN.

Project description:OBJECTIVE:To clone and express a truncated, soluble vascular endothelial growth factor receptor 2 (sVEGFR2) possessing the combined-functional domains 1-3 and 5 in eukaryotic cells and to test the inhibitory effects of full length VEGFR2 in vivo. RESULTS:pCMV6-trunctated-rVegfr2 (6100 bp) was successfully cloned. The transfection experiments showed that either pCMV6-truncated-rat-Vegfr2 (pCMV6-truncated-rVegfr2) or pCMV6-rVegfr2 inhibited the expression of intracellular green fluorescent protein, which is usually used as an exogenous transfected reporter gene to determine the transfected efficiency. An analysis of the transfected cells revealed that the amount of full-length VEGFR2 protein in the pCMV6-truncated-rVegfr2 transfected cells was 20% lower than that in the negative control (non-transfected HEK 293 cells). The differences in test results between the transfected and negative control groups were greatest from 24-30 h after transfection; this period was therefore chosen as optimal for collecting culture supernatants. This analysis was highly sensitive for detecting the amount of sVEGFR2 protein expressed and secreted by the cells, and the sVEGFR2 protein content was found to increase by approximately 26% in the transfected cells compared to that in the negative control cells (68.2% ± 1.7% vs. 41.9% ± 2.9%, P = 0.000) and by 18% compared to the negative control cells (68.2% ± 1.7% vs. 50.0% ± 0.5%, P = 0.003). Propidium iodide and Hoechst staining indicated no significant change in the number of HEK293 cells undergoing apoptosis 6 days after pCMV6-trucated-Vegfr2 transfection, compared to the negative control. Soluble VEGFR2 produced by pCMV6-truncated-rVegfr2 inhibited full-length VEGFR2 protein expression in the cell membrane. CONCLUSIONS:This study employed a eukaryotic system to express sVEGFR2. The use of transient transfection technology greatly improved transfect efficiency. Recombinant sVEGFR2 inhibited the effect of endogenous full-length VEGFR2 but was not cytotoxic.

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AUF1-RGG peptides up-regulate the VEGF antagonist, soluble VEGF receptor-1 (sFlt-1).

Publications

AUF1-RGG peptides up-regulate the VEGF antagonist, soluble VEGF receptor-1 (sFlt-1).

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