Deferoxamine produces nitric oxide under ferricyanide oxidation, blood incubation, and UV-irradiation

Activating Angiogenesis and Immunoregulation to Propel Bone Regeneration via Deferoxamine-Laden Mg-Mediated Tantalum Oxide Nanoplatform

Vascularization and inflammation management are essential for successful bone regeneration during the healing process of large bone defects assisted by artificial implants/fillers. Therefore, this study is devoted to the optimization of the osteogenic microenvironment for accelerated bone healing through rapid neovascularization and appropriate inflammation inhibition that were achieved by applying a tantalum oxide (TaO)-based nanoplatform carrying functional substances at the bone defect. Specifically, TaO mesoporous nanospheres were first constructed and then modified by functionalized metal ions (Mg2+) with the following deferoxamine (DFO) loading to obtain the final product simplified as DFO-Mg-TaO. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that the product was homogeneously dispersed hollow nanospheres with large specific surface areas and mesoporous shells suitable for loading Mg2+ and DFO. The biological assessments indicated that DFO-Mg-TaO could enhance the adhesion, proliferation, and osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). The DFO released from DFO-Mg-TaO promoted angiogenetic activity by upregulating the expressions of hypoxia-inducible factor-1 (HIF-1α) and vascular endothelial growth factor (VEGF). Notably, DFO-Mg-TaO also displayed anti-inflammatory activity by reducing the expressions of pro-inflammatory factors, benefiting from the release of bioactive Mg2+. In vivo experiments demonstrated that DFO-Mg-TaO integrated with vascular regenerative, anti-inflammatory, and osteogenic activities significantly accelerated the reconstruction of bone defects. Our findings suggest that the optimized DFO-Mg-TaO nanospheres are promising as multifunctional fillers to speed up the bone healing process.

Artifacts Introduced by Sample Handling in Chemiluminescence Assays of Nitric Oxide Metabolites

We recently developed a combination of four chemiluminescence-based assays for selective detection of different nitric oxide (NO) metabolites, including nitrite, S-nitrosothiols (SNOs), heme-nitrosyl (heme-NO), and dinitrosyl iron complexes (DNICs). However, these NO species (NOx) may be under dynamic equilibria during sample handling, which affects the final determination made from the readout of assays. Using fetal and maternal sheep from low and high altitudes (300 and 3801 m, respectively) as models of different NOx levels and compositions, we tested the hypothesis that sample handling introduces artifacts in chemiluminescence assays of NOx. Here, we demonstrate the following: (1) room temperature placement is associated with an increase and decrease in NOx in plasma and whole blood samples, respectively; (2) snap freezing and thawing lead to the interconversion of different NOx in plasma; (3) snap freezing and homogenization in liquid nitrogen eliminate a significant fraction of NOx in the aorta of stressed animals; (4) A "stop solution" commonly used to preserve nitrite and SNOs leads to the interconversion of different NOx in blood, while deproteinization results in a significant increase in detectable NOx; (5) some reagents widely used in sample pretreatments, such as mercury chloride, acid sulfanilamide, N-ethylmaleimide, ferricyanide, and anticoagulant ethylenediaminetetraacetic acid, have unintended effects that destabilize SNO, DNICs, and/or heme-NO; (6) blood, including the residual blood clot left in the washed purge vessel, quenches the signal of nitrite when using ascorbic acid and acetic acid as the purge vessel reagent; and (7) new limitations to the four chemiluminescence-based assays. This study points out the need for re-evaluation of previous chemiluminescence measurements of NOx, and calls for special attention to be paid to sample handling, as it can introduce significant artifacts into NOx assays.

Designing Deferoxamine-Loaded Flaxseed Gum and Carrageenan-Based Controlled Release Biocomposite Hydrogel Films for Wound Healing

In this study, biocomposite hydrogel films made from flaxseed gum (FSG)/kappa carrageenan (CGN) were fabricated, using potassium chloride as a crosslinker and glycerol as a plasticizer. The composite films were loaded with deferoxamine (DFX), an iron chelator that promotes neovascularization and angiogenesis for the healing of wounds. The properties of the biocomposite hydrogel films, including swelling, solubility, water vapor transmission rate, tensile strength, elongation at break, and Young’s modulus studies, were tested. The films were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). In addition, drug release studies in PBS at pH 7.2 were investigated. In vivo analysis was performed by assessing the wound contraction in a full-thickness excisional wound rat model. Hematoxylin & eosin (H & E) and Masson’s trichome staining were performed to evaluate the effect of the films on wound healing progress. The visual and micro-morphological analysis revealed the homogenous structure of the films; however, the elongation at break property decreased within the crosslinked film but increased for the drug-loaded film. The FTIR analysis confirmed the crosslinking due to potassium chloride. A superior resistance towards thermal degradation was confirmed by TGA for the crosslinked and drug-loaded films. Drug release from the optimum film was sustained for up to 24 h. In vivo testing demonstrated 100% wound contraction for the drug-loaded film group compared to 72% for the pure drug solution group. In light of the obtained results, the higher potential of the optimized biocomposite hydrogel film for wound healing applications was corroborated.

Iron nitrosyl complexes are formed from nitrite in the human placenta

Placental nitric oxide (NO) is critical for maintaining perfusion in the maternal-fetal-placental circulation during normal pregnancy. NO and its many metabolites are also increased in pregnancies complicated by maternal inflammation such as preeclampsia, fetal growth restriction, gestational diabetes, and bacterial infection. However, it is unclear how increased levels of NO or its metabolites affect placental function, or how the placenta deals with excessive levels of NO or its metabolites. Since there is uncertainty over the direction of change in plasma levels of NO metabolites in preeclampsia, we measured the levels of these metabolites at the placental tissue level. We found that NO metabolites are increased in placentas from patients with preeclampsia compared to healthy controls. We also discovered by ozone-based chemiluminescence and electron paramagnetic resonance that nitrite is efficiently converted into iron nitrosyl complexes (FeNOs) within the human placenta, and also observed the existence of endogenous FeNOs within placentas from sheep and rats. We show these nitrite-derived FeNOs are relatively short-lived, predominantly protein-bound, heme-iron nitrosyl complexes. The efficient formation of FeNOs from nitrite in the human placenta hints towards the importance of both nitrite and iron nitrosyl complexes in placental physiology or pathology. As iron nitrosylation is an important post-translational modification that affects the activity of multiple iron-containing proteins such as those in the electron transport chain, or those involved in epigenetic regulation, we conclude that FeNOs merit increased study in pregnancy complications.