ATP-dependent stabilization and protection of fibroblast growth factor 2

Integration of Zn2+, ATP, and bFGF to Nanodressing with Core-Shell Structure Fabricated by Emulsion Electrospinning for Wound Healing

Basic fibroblast growth factor (bFGF) plays an important role in active wound repair. However, the existing dosage forms in clinical applications are mainly sprays and freeze-dried powders, which are prone to inactivation and cannot achieve a controlled release. In this study, a bioactive wound dressing named bFGF-ATP-Zn/polycaprolactone (PCL) nanodressing with a "core-shell" structure was fabricated by emulsion electrospinning, enabling the sustained release of bFGF. Based on the coordination and electrostatic interactions among bFGF, ATP, and Zn2+, as well as their synergistic effect on promoting wound healing, a bFGF-ATP-Zn ternary combination system was prepared with higher cell proliferation activity and used as the water phase for emulsion electrospinning. The bFGF-ATP-Zn/PCL nanodressing demonstrated improved mechanical properties, sustained release of bFGF, cytocompatibility, and hemocompatibility. It increased the proliferation activity of human dermal fibroblasts (HDFs) and enhanced collagen secretion by 1.39 and 3.45 times, respectively, while reducing the hemolysis rate to 3.13%. The application of the bFGF-ATP-Zn/PCL nanodressing in mouse full-thickness skin defect repair showed its ability to accelerate wound healing and reduce wound scarring within 14 days. These results provide a research basis for the development and application of this bioactive wound dressing product.

Camelina lipid droplets as skin delivery system promotes wound repair by enhancing the absorption of hFGF2

Human basic fibroblast growth factor (hFGF2) is widely recognized for accelerating skin wound healing in both animal models and randomized clinical trials. However, the low skin permeation and bioavailability of hFGF2 remain the most limiting factors in the pharmacological application. For the first time, Camelina Lipid Droplets (CLD) delivery system was displayed important virtue, by promoting the skin absorption of hFGF2, which is a key factor that accelerates the skin wound repair, and provide a new alternative for skin therapy. In this study, we used the CLD as a safer material to prepare the nanoparticles, which were characterized by size and morphology. Our data revealed that particle sizes of Camelina Lipid Droplets linked to hFGF2 (CLD-hFGF2) were around 133.5 nm; it also displayed that the complex of CLD-hFGF2 penetrates the skin barrier in deeper than an individual hFGF2. This suggests that once the hFGF2 is fixed onto the surface of CLD, it can cross the stratum corneum and play a therapeutic role into the dermis. Furthermore, we demonstrated that CLD-hFGF2 enhances fibroblast migration, and significantly improves skin regeneration for accelerating wound healing without any significant toxicity. This paper highlights the importance of CLD as an emerging delivery system; it is also providing a new and applicable therapeutic research direction through enhancing the skin permeation of hFGF2 to accelerate wound healing.

Foscarnet reduces FGF2-induced proliferation of human umbilical vein endothelial cells and has antineoplastic activity against human anaplastic thyroid carcinoma cells

In contrast to many reports dealing with inhibitors of growth factor receptors like VEGF or FGFR, only few reports of low molecular weight inhibitors, which are directed against growth factors itself, are known. Here, foscarnet, an antiviral drug which inhibits several viral DNA polymerases by mimic pyrophosphate of nucleotides, was identified to interact with fibroblast growth factor 2 and stabilize the growth factor against tryptic digestion similar like the non-nitrogen containing bisphosphonates clodronate and etidronate that we have reported just recently as inhibitors of FGF-induced cell proliferation. Foscarnet competes with ATP against the binding on fibroblast growth factor 2 at the heparin/ATP-binding domain. This indicates binding of foscarnet at the heparin-binding domain of FGF2. This interaction of foscarnet with fibroblast growth factor 2 reduces FGF2-induced proliferation of human umbilical vein endothelial cells and intracellular signaling via ERK1/2 kinases in this cell line. Additionally, foscarnet reduces in a dose-dependent manner proliferation of CAL-62 cells that belong to anaplastic thyroid carcinoma, a rare but lethal type of thyroid cancer that expresses FGF2.

Structural and Functional Characterization of RecG Helicase under Dilute and Molecular Crowding Conditions

In an ATP-dependent reaction, the Escherichia coli RecG helicase unwinds DNA junctions in vitro. We present evidence of a unique protein conformational change in the RecG helicase from an α-helix to a β-strand upon an ATP binding under dilute conditions using circular dichroism (CD) spectroscopy. In contrast, under molecular crowding conditions, the α-helical conformation was stable even upon an ATP binding. These distinct conformational behaviors were observed to be independent of Na⁺ and Mg²⁺. Interestingly, CD measurements demonstrated that the spectra of a frayed duplex decreased with increasing of the RecG concentration both under dilute and molecular crowding conditions in the presence of ATP, suggesting that RecG unwound the frayed duplex. Our findings raise the possibility that the α-helix and β-strand forms of RecG are a preactive and an active structure with the helicase activity, respectively.

The most negatively charged low-density lipoprotein L5 induces stress pathways in vascular endothelial cells

BACKGROUND/AIMS

L5, the most negatively charged species of low-density lipoprotein (LDL), has been implicated in atherogenesis by inducing apoptosis of endothelial cells (ECs) and inhibiting the differentiation of endothelial progenitor cells. In this study, we compared the effects of LDL charge on cellular stress pathways leading to atherogenesis.

METHODS

We isolated L5 and L1 (the least negatively charged LDL) from the plasma of patients with familial hypercholesterolemia and used JC-1 staining to examine the effects of L5 and L1 on the mitochondrial membrane potential (DCm) in human umbilical vein ECs (HUVECs). Additionally, we characterized the gene expression profiles of 7 proteins involved in various types of cellular stress.

RESULTS

The DCm was severely compromised in HUVECs treated with L5. Furthermore, compared with L1, L5 induced a decrease in mRNA and protein expression of the endoplasmic reticulum (ER) chaperone proteins ORP150, Grp94, and Grp58, mitochondrial proteins Prdx3 and ATP synthase, and an increase in the expression of the pro-inflammatory protein hnRNP C1/C2.

CONCLUSIONS

Our work suggests that L5, but not L1, may promote the destruction of ECs that occurs during atherogenesis by causing mitochondrial dysfunction and modulating the expression of key proteins to promote inflammation, ER dysfunction, oxidative stress, and apoptosis.

ATP-NGF-complex, but not NGF, is the neuroprotective ligand

We have shown previously that nerve growth factor (NGF) requires only low nanomolar ATP concentrations in the cell culture medium to protect cortical rat neurons (CRN) from cellular damage induced by staurosporine (STS). We have also demonstrated before that NGF and other growth factors form stable non-covalent complexes with ATP. Here we demonstrated that 8N(1)ATP-NGF, but not NGF, protected CRN against damage. The photo-reactive ATP derivative 8N(3)ATP was incubated with NGF and was trapped in its position by UV irradiation forming a covalent bond. The cross-link with a molar ratio of 1:1 (8N(1)ATP:NGF) was confirmed by mass spectrometry. Circular dichroism experiments revealed that 8N(1)ATP altered the secondary structure of NGF in the same way as ATP did. Covalently bound 8N(1)ATP-NGF was shown to be stable in the presence of the ATP-hydrolyzing enzyme alkaline phosphatase while the non-covalent ATP-NGF-complex dissociated with the removal of free ATP from the solution. 8N(1)ATP-NGF protected CRN against damage by STS independently of free ATP in the culture medium. These results suggest that the ATP-NGF-complex, but not NGF, is the active ligand.

Binding of ATP to vascular endothelial growth factor isoform VEGF-A165 is essential for inducing proliferation of human umbilical vein endothelial cells

BACKGROUND

ATP binding is essential for the bioactivity of several growth factors including nerve growth factor, fibroblast growth factor-2 and brain-derived neurotrophic factor. Vascular endothelial growth factor isoform 165 (VEGF-A(165)) induces the proliferation of human umbilical vein endothelial cells, however a dependence on ATP-binding is currently unknown. The aim of the present study was to determine if ATP binding is essential for the bioactivity of VEGF-A(165).

RESULTS

We found evidence that ATP binding to VEGF-A(165) induced a conformational change in the secondary structure of the growth factor. This binding appears to be significant at the biological level, as we found evidence that nanomolar levels of ATP (4-8 nm) are required for the VEGF-A(165)-induced proliferation of human umbilical vein endothelial cells. At these levels, purinergic signaling by ATP via P2 receptors can be excluded. Addition of alkaline phosphate to cell culture lowered the ATP concentration in the cell culture medium to 1.8 nM and inhibited cell proliferation.

CONCLUSIONS

We propose that proliferation of endothelial cells is induced by a VEGF-A(165)-ATP complex, rather than VEGF-A(165) alone.

Interaction of ATP with fibroblast growth factor 2: biochemical characterization and consequence for growth factor stability

Background

Fibroblast growth factor 2, a well-characterized heparin-binding growth factor, is involved in many biological processes like embryogenesis, cell proliferation and angiogenesis. However, this growth factor is very unstable and shows rapid degradation in aqueous solution. Beside the well-known stabilization of FGF2 by heparin or heparan sulphate, the recently discovered binding to ATP also shows a stabilizing and protective effect on this growth factor.

Results

Here we determined the dissociation constant of ATP on FGF2 by equilibrium microdialysis (K_D: 59.8 μM) and analyzed the impact of this binding on secondary structure by CD-spectroscopy. ATP-binding to FGF2 significantly changed the secondary structure of this growth factor with a shift to random coil structure elements. We also analyzed the influence of this binding on the stability of FGF2 in aqueous solution over a period of 2 h. While the amount of untreated FGF2 is reduced drastically over this period of time, ATP-binding reduces the degradation considerably.

Conclusions

Taken together, our data suggest an important role of ATP in FGF2-stabilization beside the well known-role of heparin and heparan sulphate.

Interaction of clodronate with fibroblast growth factor 2 reduces FGF2-activity in endothelial cells

Stabilization of fibroblast growth factors from heat denaturation and proteolytic digestion by bound heparin and heparan sulphate proteoglycans is known for more than 20 years. Furthermore, ATP-binding to FGF2 also leads to stabilization of this growth factor as discovered recently. The physiological importance of this protection is not yet clear but has become the focal point of interest. In this study we used the method of stabilizing FGF2 from proteolytic degradation to identify some bisphosphonates, namely clodronate and etidronate, which interact with FGF2. These two bisphoshonates protect FGF2 from tryptic digestion in vitro. The circular dichroism spectrum of FGF2 incubated with clodronate was significantly shifted compared to the spectrum of non-treated FGF2 indicating a conformational change of the protein after clodronate-binding. Additionally, clodronate and etidronate at low μM concentrations induce a concentration-dependent reduction of FGF2-induced cell proliferation of human umbilical vein endothelial cells. In contrast, proliferation of these cells after addition of clodronate and etidronate without FGF2 was not influenced by these bisphosphonates. Furthermore, the intracellular signaling via ERK1/2 and AKT was inhibited by clodronate and the tube formation, indicating the beginning process of angiogenesis, was reduced. Our results show for the first time that bisphosphonates I) interact with FGF2, II) reduce FGF2-activity and III) decrease the angiogenic potential of this growth factor.