Fructose-1,6-bisphosphate and N-acetylcysteine attenuate the formation of advanced oxidation protein products, a new class of inflammatory mediators, in vitro

Biomolecule-assisted green synthesis of nanostructured calcium phosphates and their biomedical applications

Calcium phosphates (CaPs) are ubiquitous in nature and vertebrate bones and teeth, and have high biocompatibility and promising applications in various biomedical fields. Nanostructured calcium phosphates (NCaPs) are recognized as promising nanocarriers for drug/gene/protein delivery owing to their high specific surface area, pH-responsive degradability, high drug/gene/protein loading capacity and sustained release performance. In order to control the structure and surface properties of NCaPs, various biomolecules with high biocompatibility such as nucleic acids, proteins, peptides, liposomes and phosphorus-containing biomolecules are used in the synthesis of NCaPs. Moreover, biomolecules play important roles in the synthesis processes, resulting in the formation of various NCaPs with different sizes and morphologies. At room temperature, biomolecules can play the following roles: (1) acting as a biocompatible organic phase to form biomolecule/CaP hybrid nanostructured materials; (2) serving as a biotemplate for the biomimetic mineralization of NCaPs; (3) acting as a biocompatible modifier to coat the surface of NCaPs, preventing their aggregation and increasing their colloidal stability. Under heating conditions, biomolecules can (1) control the crystallization process of NCaPs by forming biomolecule/CaP nanocomposites before heating; (2) prevent the rapid and disordered growth of NCaPs by chelating with Ca2+ ions to form precursors; (3) provide the phosphorus source for the controlled synthesis of NCaPs by using phosphorus-containing biomolecules. This review focuses on the important roles of biomolecules in the synthesis of NCaPs, which are expected to guide the design and controlled synthesis of NCaPs. Moreover, we will also summarize the biomedical applications of NCaPs in nanomedicine and tissue engineering, and discuss their current research trends and future prospects.

Preparation of porous calcium phosphate microspheres with phosphate-containing molecules at room temperature for drug delivery and osteogenic differentiation

Calcium phosphate (CaP) has similar chemical properties to those of the inorganic component of human bone tissue, for potential application in drug delivery for the chemotherapy of osteosarcoma. In this work, CaP with a porous microsphere structure has been synthesized using fructose-1,6-bisphosphate (FBP) as the phosphorus source by a simple wet-chemical strategy at room temperature. The CaP porous microspheres, as an organic–inorganic hybrid nano-platform, exhibit good doxorubicin (Dox) loading capacity, and Dox-loading CaP, enhancing the in vitro chemotherapy of osteosarcoma cells. The CaP porous microspheres show high biocompatibility, and induce the osteogenic differentiation of MC3T3-E1. These results indicate that the CaP porous microspheres reported in this study are promising for application as an anti-osteosarcoma drug carrier and osteoinductive material for bone regeneration in the treatment of osteosarcoma.

Porous calcium phosphate microspheres were prepared at room temperature, and displayed potential for application in the chemotherapy of osteosarcoma and osteogenic differentiation.

The Characteristics and Roles of Advanced Oxidation Protein Products in Atherosclerosis

Advanced oxidation protein products (AOPPs) are novel biomarkers of oxidative damage to proteins and a novel class of inflammatory mediators. AOPPs can promote oxidative stress (OS) and inflammation and thus participate in many pathophysiological disease processes. Atherosclerosis is a chronic inflammatory disease of blood vessels that is characterized by low-density lipoprotein infiltration into the endothelial intima and the formation of atherosclerotic plaques. Inflammation and OS are established risk factors for the formation of atherosclerosis. Accumulated studies show that AOPPs can accelerate the progression of atherosclerosis through OS and inflammation. Additionally, AOPPs can accelerate the formation of atherosclerotic plaques by inhibiting high-density lipoprotein receptor scavenger receptor class B type I-mediated high-density lipoprotein cholesterol reverse transport, leading to metabolic disturbances. Some studies have suggested that plasma AOPPs levels are independently positively correlated with blood pressure and are also independent risk factors for cardiovascular disease. AOPPs can trigger oxidative bursts of neutrophils, monocytes and phagocytic cells, increase the generation of reactive oxygen species and promote the secretion of cytokines to accelerate endothelial cell injury. Detecting the levels and inhibiting the formation of AOPPs may provide a novel approach to monitor the progress and improve the prognosis of atherosclerosis.

In vitro oxidation of fibrinogen promotes functional alterations and formation of advanced oxidation protein products, an inflammation mediator

Fibrinogen (FB) is a soluble blood plasma protein and is a key molecule involved in coagulation. Oxidative modification of proteins, such as the formation of advanced oxidation protein products (AOPP), a heterogeneous family of protein compounds structurally modified and derived from oxidative stress, may be associated with the pathophysiology of a number of chronic inflammatory diseases. Therefore, the aim of this study was to determine whether the formation of this mediator of inflammation occurs from FB and whether its generation is associated with structural changes. Results of the present study suggest that the oxidation of FB may provoke the formation of AOPP, which in turn, may promote functional alterations in FB, thus causing changes in its structural domains and increasing its procoagulant activity.

Magnesium whitlockite hollow microspheres: a comparison of microwave-hydrothermal and conventional hydrothermal syntheses using fructose 1,6-bisphosphate, and application in protein adsorption

Magnesium whitlockite hollow microspheres with high biocompatibility and protein adsorption capacity are synthesized by a rapid microwave-hydrothermal method using fructose 1,6-bisphosphate.

Correlations between peroxisome proliferator activator receptor γ, Cystatin C, or advanced oxidation protein product, and atherosclerosis in diabetes patients

We aimed to explore the relationship between peroxisome proliferator activator receptor γ (PPAR γ), Cystatin C or advanced oxidation protein product (AOPP) and atherosclerosis (AS), and identify their diagnostic values for AS. Eighty AS patients above the age of 75 with type 2 diabetes were screened by brachial-ankle pulse wave velocity (baPWV) and ankle brachial index (ABI). The baseline level of patients was firstly analyzed, and then the expression of PPAR γ was detected by reverse transcriptase-polymerase chain reaction (RT-PCR). Meanwhile, a double-antibody sandwich enzyme-linked immunosorbent assay was performed to analyze the concentration of AOPP, and immunonephelometry was carried out to detect the concentration of Cystatin C. The baseline level of patients was basically consistent. The expression of PPAR γ was significantly higher in severe AS than mild AS patients (P < 0.05), while no differences were found in serum Cystatin C and AOPP between severe AS and mild AS patients (P > 0.05). Thus, PPAR γ exhibited a high diagnostic value for severe AS (AUC = 0.850), but not Cystatin C and AOPP (AUC = 0.553, AUC = 0.4780). Moreover, the combination of PPAR γ, Cystatin C and AOPP exhibited a quite high diagnostic value in AS (AUC = 0.961, Sen = 0.9, Spe = 0.975), which was also higher than PPAR γ alone. In conclusion, the contents of PPAR γ, Cystatin C and AOPP were closely related to AS in diabetes, indicating a potential clinical diagnostic value of PPAR γ, Cystatin C and AOPP in diabetes with AS.

An alternative pathway through the Fenton reaction for the formation of advanced oxidation protein products, a new class of inflammatory mediators

The accumulation of advanced oxidation protein products (AOPPs) has been linked to several pathological conditions, and their levels are formed during oxidative stress as a result of reactions between plasma proteins and chlorinated oxidants produced by myeloperoxidase (MPO). However, it was suggested that the generation of this mediator of inflammation may also occur via an MPO-independent pathway. The aim of this study was to induce the formation of AOPPs in vitro through Fenton reaction and to investigate whether this generation could be counteracted by N-acetylcysteine (NAC) and fructose-1,6-bisphosphate (FBP). The complete Fenton system increased the AOPPs levels and both NAC and FBP were capable of inhibiting the formation of Fenton reaction-induced AOPPs. These data provide a new hypothesis about another pathway of AOPPs formation, as well as report that NAC and FBP may be good candidates to neutralize pro-inflammatory and pro-oxidant effects of AOPPs in several diseases.

Advanced oxidation protein products and ischaemia-modified albumin in obstructive sleep apnea

BACKGROUND

Several studies have shown that obstructive sleep apnea increases incidence of cardiovascular morbidity and mortality. The high systemic oxidative stress in obstructive sleep apnea has been considered as a major pathogenic mechanism leading to cardiovascular disease. Oxidative stress-related lipid and DNA oxidation in obstructive sleep apnea have been reported in the previous studies. In contrast, there is limited and contradictory information regarding protein oxidation in obstructive sleep apnea patients such as ischaemia-modified albumin and advanced oxidation protein products. Therefore, we aimed to investigate plasma ischaemia-modified albumin and advanced oxidation protein products and their correlation with total oxidative status and total antioxidative capacity in the obstructive sleep apnea patients.

METHODS

Plasma ischaemia-modified albumin, advanced oxidation protein products, total oxidative status and total antioxidative capacity were measured in 25 healthy volunteers and 59 obstructive sleep apnea patients diagnosed with polysomnography.

RESULTS

Plasma total antioxidative capacity was significantly lower (P = 0·012) and total oxidative status was significantly higher (P < 0·001) in the patients compared to the controls demonstrating increased oxidative stress in the patients. Plasma advanced oxidation protein products were significantly higher in the patients than the controls (P = 0·024). Plasma ischaemia-modified albumin levels were not statistically different between the obstructive sleep apnea patients and controls (P = 0·74).

CONCLUSIONS

We conclude that high systemic oxidative stress in obstructive sleep apnea is reflected by increased advanced oxidation protein products without causing an increase in ischaemia-modified albumin.